The Carboxyl Terminus of Protein Kinase C Provides a Switch to Regulate Its Interaction with the Phosphoinositide-dependent Kinase, PDK-1

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The function of protein kinase C family members depends on two tightly coupled phosphorylation mechanisms: phosphorylation of the activation loop by the phosphoinositide-dependent kinase, PDK-1, followed by autophosphorylation at two positions in the COOH terminus, the turn motif, and the hydrophobic motif. Here we address the molecular mechanisms underlying the regulation of protein kinase C βII by PDK-1. Co-immunoprecipitation studies reveal that PDK-1 associates preferentially with its substrate, unphosphorylated protein kinase C, by a direct mechanism. The exposed COOH terminus of protein kinase C provides the primary interaction site for PDK-1, with co-expression of constructs of the carboxyl terminus effectively disrupting the interaction in vivo. Disruption of this interaction promotes the autophosphorylation of protein kinase C, suggesting that the binding of PDK-1 to the carboxyl terminus protects it from autophosphorylation. Studies with constructs of the COOH terminus reveal that the intrinsic affinity of PDK-1 for phosphorylated COOH terminus is over an order of magnitude greater than that for unphosphorylated COOH terminus, contrasting with the finding that PDK-1 does not bind phosphorylated protein kinase C effectively. However, effective binding of the phosphorylated species can be induced by the activated conformation of protein kinase C. This suggests that the carboxyl terminus becomes masked following autophosphorylation, a process that can be reversed by the conformational changes accompanying activation. Our data suggest a model in which PDK-1 provides two points of regulation of protein kinase C: 1) phosphorylation of the activation loop, which is regulated by the intrinsic activity of PDK-1, and 2) phosphorylation of the carboxyl terminus, which is regulated by the release of PDK-1 to allow autophosphorylation. The function of protein kinase C family members depends on two tightly coupled phosphorylation mechanisms: phosphorylation of the activation loop by the phosphoinositide-dependent kinase, PDK-1, followed by autophosphorylation at two positions in the COOH terminus, the turn motif, and the hydrophobic motif. Here we address the molecular mechanisms underlying the regulation of protein kinase C βII by PDK-1. Co-immunoprecipitation studies reveal that PDK-1 associates preferentially with its substrate, unphosphorylated protein kinase C, by a direct mechanism. The exposed COOH terminus of protein kinase C provides the primary interaction site for PDK-1, with co-expression of constructs of the carboxyl terminus effectively disrupting the interaction in vivo. Disruption of this interaction promotes the autophosphorylation of protein kinase C, suggesting that the binding of PDK-1 to the carboxyl terminus protects it from autophosphorylation. Studies with constructs of the COOH terminus reveal that the intrinsic affinity of PDK-1 for phosphorylated COOH terminus is over an order of magnitude greater than that for unphosphorylated COOH terminus, contrasting with the finding that PDK-1 does not bind phosphorylated protein kinase C effectively. However, effective binding of the phosphorylated species can be induced by the activated conformation of protein kinase C. This suggests that the carboxyl terminus becomes masked following autophosphorylation, a process that can be reversed by the conformational changes accompanying activation. Our data suggest a model in which PDK-1 provides two points of regulation of protein kinase C: 1) phosphorylation of the activation loop, which is regulated by the intrinsic activity of PDK-1, and 2) phosphorylation of the carboxyl terminus, which is regulated by the release of PDK-1 to allow autophosphorylation. phosphoinositide-dependent kinase 1 polyacrylamide gel electrophoresis protein kinase C polymerase chain reaction glutathioneS-transferase The phosphoinositide-dependent kinase (PDK-1),1 plays a pivotal role in cellular signaling by regulating the activation state of diverse protein kinases (1Toker A. Newton A. Cell. 2000; 103: 185-188Abstract Full Text Full Text PDF PubMed Scopus (367) Google Scholar). Such protein kinases contain a segment near the entrance to the active site that must be phosphorylated in order to correctly align residues for catalysis. This segment, the activation loop, typically blocks the active site in the inactive conformation and moves out following phosphorylation (2Johnson L.N. O'Reilly M. Curr. Opin. Struct. Biol. 1996; 6: 762-769Crossref PubMed Scopus (90) Google Scholar). Although some kinases (e.g. protein kinase A) are able to self-activate by autophosphorylating at the activation loop (3Yonemoto W. McGlone M.L. Taylor S.S. J. Biol. Chem. 1993; 268: 2348-2352Abstract Full Text PDF PubMed Google Scholar), a large number of kinases depend on an upstream activation loop kinase for phosphorylation. PDK-1 was originally discovered as the activation loop kinase for Akt/protein kinase B (4Alessi D.R. James S.R. Downes C.P. Holmes A.B. Gaffney P.R. Reese C.B. Cohen P. Curr. Biol. 1997; 7: 261-269Abstract Full Text Full Text PDF PubMed Google Scholar). Following on the heels of this discovery was the finding that PDK-1 is also the upstream kinase for p70 S6 kinase (5Pullen N. Dennis P.B. Andjelkovic M. Dufner A. Kozma S.C. Hemmings B.A. Thomas G. Science. 1998; 279: 707-710Crossref PubMed Scopus (731) Google Scholar, 6Alessi D.R. Kozlowski M.T. Weng Q.P. Morrice N. Avruch J. Curr. Biol. 1998; 8: 69-81Abstract Full Text Full Text PDF PubMed Scopus (519) Google Scholar) and both atypical (7Chou M.M. Hou W. Johnson J. Graham L.K. Lee M.H. Chen C.S. Newton A. Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Google Scholar, D.R. Cohen P. Science. 1998; PubMed Scopus Google Scholar) and A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar) of protein kinase C. The of PDK-1 to PDK-1 in the of a of signaling from protein to and D.R. J. 2000; PubMed Scopus Google Scholar, A. 2000; PubMed Scopus Google Scholar). by PDK-1 is the of in the of protein kinase C A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar). are to the conformation of the and to the to the Curr. Biol. 1996; 6: Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, Newton J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, Newton J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). is the phosphorylated species of protein kinase C that the of in of J. PubMed Scopus Google Scholar, Curr. Opin. Biol. 1997; PubMed Scopus Google Scholar). species of and and and typically to the to the of The interaction is by two the which and and the in in a J. Newton 2000; PubMed Scopus Google Scholar). of on the provides the to release an from the which in activation of the and studies over the two to a of protein kinase C is regulated by However, the of protein kinase C is regulated to be to the activation loop, protein kinase C is phosphorylated at two positions in the carboxyl terminus Newton Curr. Biol. Full Text Full Text PDF PubMed Scopus Google the turn in protein kinase C it to a phosphorylation site in protein kinase at the of a and the hydrophobic in protein kinase C which a by hydrophobic The phosphorylation at the activation loop that is by PDK-1 the autophosphorylation of two positions A. Newton Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). the by PDK-1 is the it is regulated is to the cellular of protein kinase C number of studies suggest that PDK-1 with affinity with its kinase protein kinase C and p70 S6 kinases are in of PDK-1 (7Chou M.M. Hou W. Johnson J. Graham L.K. Lee M.H. Chen C.S. Newton A. Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Google Scholar, D.R. Cohen P. Science. 1998; PubMed Scopus Google Scholar, A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar). PDK-1 its a in this kinase the function of its This PDK-1 and protein kinase C βII in vivo. the of PDK-1 to with constructs of protein kinase C and its in we that PDK-1 with in the hydrophobic phosphorylation of protein kinase C. The binding of PDK-1 the autophosphorylation for the of protein kinase C, with release of PDK-1 the COOH terminus for autophosphorylation. PDK-1 both phosphorylation of protein kinase C: the activation loop by direct phosphorylation and the by release from protein kinase C. from The large the of The of βII was a of of the COOH terminus of βII was from that the phosphorylated activation loop of protein kinase C was and as A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar, Johnson J. Chen Newton A. J. 1998; PubMed Scopus Google Scholar). to as by the phosphorylated in the COOH terminus of βII was from the PDK-1 in (7Chou M.M. Hou W. Johnson J. Graham L.K. Lee M.H. Chen C.S. Newton A. Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Google Scholar). The the and phosphorylation site of phosphorylation the PDK-1 site to from of to phosphorylation to that is to Newton J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). and the for in A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar, Newton J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar, Newton J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. Newton Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, Newton J. Biol. Chem. Full Text PDF PubMed Google Scholar). The the the and the COOH terminus residues of protein kinase C βII as in following of the as the the for the a site and site at the and The the and of the βII COOH terminus with the that the the The constructs the following and a the COOH terminus of A. A. M. A. Gaffney P. Downes C.P. D.R. Curr. Biol. Full Text Full Text PDF PubMed Scopus Google was from of of and the for as a protein in in and at in of was out The to the by of the as and 1 of was in the the interaction PDK-1 and of protein kinase C βII in with PDK-1 and the the the in 1 1 and The was by at and the is to as the of the was in for and the was with at for in and in B the and with of protein kinase C βII and the in A. of the was in for and the was with an and protein at the direct interaction PDK-1 and protein kinase C with PDK-1 protein kinase C The PDK-1 and protein kinase C βII as Newton J. Biol. Chem. Full Text PDF PubMed Google Scholar). The of protein kinase C was by of protein kinase C βII with for at in the of 1 as Newton J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). The in and with an in the of at for The in and in The in the and that PDK-1 and protein kinase C βII in as by studies in with the for kinase A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar). the of this interaction and it is we the of protein kinase C that the and the interaction is by the phosphorylation state and activation state of protein kinase C. 1 the constructs of PDK-1 and protein kinase C in this PDK-1 and protein kinase C βII in and the of the was to the that a of the protein kinase C with PDK-1, with A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar). species of protein kinase C in the a by which phosphorylated protein kinase C Newton Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar) and was by the loop not and a species with a which unphosphorylated protein kinase C and was not by the The species in the was to the in the of a of the species to the phosphorylated species in the with the of species in the PDK-1 unphosphorylated protein kinase C. the interaction of protein kinase C with PDK-1 was direct by a we the interaction of PDK-1 with protein kinase C. in and to that protein kinase C βII was in with PDK-1 the was in the unphosphorylated species of protein kinase C: this species was in the in the The of of protein kinase C by PDK-1 in in was suggesting that direct interaction of the two was the primary for the interaction in vivo. The that PDK-1 preferentially associates with its substrate, unphosphorylated protein kinase C with the phosphorylated protein kinase C This species is phosphorylated at the activation loop, and and the carboxyl the phosphorylation at positions of protein kinase C with PDK-1, we the of constructs at for the to an with PDK-1. The with the to PDK-1 and the for protein kinase C. that the of PDK-1 was the B a of the and phosphorylation site of protein kinase C βII in protein kinase C 1) as a to the in both the and with unphosphorylated protein kinase C by that of to to kinase activity and in of protein kinase C Newton J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Newton J. Biol. Chem. Full Text PDF PubMed Google Newton J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). is a for PDK-1, it is and not Newton J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of to in the of a and a by This is with studies that of to on the activity of protein kinase C that the of the that in the is phosphorylated at and this phosphorylated species at an of with in phosphorylation of protein kinase C that the is a of and with that the and constructs effectively with PDK-1 the with of that and as and in with unphosphorylated protein kinase C The of protein with at suggests that the at the the of protein kinase C by PDK-1. at regulated the interaction of protein kinase C with PDK-1, we the of PDK-1 to with the and in vivo. the of species by the in the with PDK-1 This species protein kinase C phosphorylated at the activation loop and of the of from the with PDK-1 was than the of protein kinase C that was data suggest that of with in a in the affinity of protein kinase C for PDK-1. PDK-1 was also able to effectively the the as the species with the phosphorylated protein kinase C βII The of that with PDK-1 was to the of phosphorylated protein kinase C βII that with PDK-1 1 and of that the of to protein kinase C in was protein kinase C with a at with PDK-1, protein kinase C with a at with PDK-1 than protein with at that reveal that PDK-1 preferentially the unphosphorylated conformation of protein kinase C. the of in this we the of the and of protein kinase C βII to with PDK-1 to the interaction of PDK-1 with protein kinase C βII in vivo. we on a of constructs of the residues to the role of the hydrophobic phosphorylation in the kinase C constructs and also the interaction with a of to bind with affinity to PDK-1 A. A. M. A. Gaffney P. Downes C.P. D.R. Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). with PDK-1 and the protein constructs and the interaction with PDK-1 was by the of The protein of PDK-1 was in the B that constructs of the COOH terminus, in and effectively by as by with the of the COOH terminus and of and the effective at PDK-1. on the PDK-1 in the of the protein in the of data from that PDK-1 than the COOH terminus of protein kinase C to the the constructs of the COOH terminus interaction with PDK-1 and in which the two to not with PDK-1 of the the kinase and the COOH terminus was in the was with PDK-1 The constructs of the and in and binding of PDK-1 to the not to the and data suggest that the kinase and in the COOH terminus, the primary in the interaction of protein kinase C with PDK-1, with some of the B that the protein as on suggesting by phosphorylation. of the in the of a and are and on the and constructs as with the with the two and 1) and the with the two 1 and a in which both and to as a was the as that of the of the This suggests that a of the becomes phosphorylated at in vivo. an that phosphorylated that the two and of the COOH terminus phosphorylated on C, This not the a C, and data reveal that a of the COOH terminus is phosphorylated on and an on and The is effectively phosphorylated in by protein kinase C suggesting that the phosphorylation of this in be by protein kinase C not the that the COOH terminus of protein kinase C is a in the interaction of PDK-1 with protein kinase C, we the of the constructs of the COOH terminus, to the interaction of PDK-1 with protein kinase C βII in vivo. with PDK-1 and protein kinase C, and the PDK-1 was from the and the of protein kinase C was by that protein kinase C was to in and the of PDK-1 in the was the protein kinase C in the as a species phosphorylated of PDK-1 from with protein kinase C and in of protein kinase C co-expression of the of protein kinase C βII with PDK-1 to co-expression of a in the of protein kinase C with PDK-1 the and constructs on the kinase C interaction the finding that the was effective in disrupting the interaction of PDK-1 with protein kinase C in that the constructs with the we that the species in disrupting the interaction was the phosphorylated we the phosphorylated was with PDK-1 in the in A. B that two constructs in of PDK-1 as by the the COOH terminus and and the species of in the was phosphorylated at as by with the and its with the species of the The species not that phosphorylation of the COOH terminus effective in disrupting the interaction of PDK-1 with protein kinase C. The protein kinase C and the to in not with the of phosphorylated of the B and the of protein kinase C to phosphorylated was The of the to the kinase C the of protein kinase C, suggests that it a affinity for PDK-1 than the protein kinase C. the that phosphorylated PDK-1 with affinity with the unphosphorylated we a PDK-1 and PDK-1 was from the and the phosphorylation state of the with the was The of and PDK-1 was in the with the as in the However, the species of phosphorylated on was with PDK-1 as by its with the and data that PDK-1 the protein of The data reveal that PDK-1 unphosphorylated protein kinase C with phosphorylated protein kinase C studies with the COOH terminus that the intrinsic affinity of PDK-1 is greater for constructs that are phosphorylated at and protein kinase C conformational changes following we the that the COOH terminus of protein kinase C becomes masked following the of the that the of protein kinase C is exposed in the unphosphorylated conformation of protein kinase C, masked in the phosphorylated inactive and exposed following activation Newton J. Biol. Chem. Full Text PDF PubMed Google Scholar, Newton J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). This to the conformation of activated protein kinase C the COOH terminus and binding of PDK-1. kinase C was activated by with a that promotes the conformation of protein kinase C Newton J. Biol. Chem. Full Text PDF PubMed Google Scholar). that in a in the of protein kinase C βII in with PDK-1. This was for protein kinase C: the kinase of protein kinase C with PDK-1 in the of in binding of protein kinase C to PDK-1 was following activation by not data suggest that the conformation induced by binding the binding of PDK-1, by the the kinase is not masked by the with in the not be to the conformation of the COOH terminus of the kinase the of co-expression of the COOH terminus of protein kinase C on the autophosphorylation of the protein kinase C, with βII and PDK-1 in the of the the in protein kinase C βII as a in with the species by a unphosphorylated protein kinase C and the species phosphorylated with the data in of the the interaction of PDK-1 with protein kinase C the was the species of protein kinase C in the was to the with 1 and the the of protein kinase C. data suggest that release of PDK-1 from protein kinase C of the COOH terminus promotes the autophosphorylation which the Co-immunoprecipitation studies reveal that PDK-1 associates preferentially with its substrate, unphosphorylated protein kinase C. of of protein kinase C that the primary that the interaction of protein kinase C with PDK-1 in the COOH terminus of protein kinase C, with the in the is the COOH terminus of protein kinase C provides a for binding PDK-1, and constructs of this PDK-1 from unphosphorylated protein kinase C, its two points of regulation of protein kinase C by by the activation loop, and by the autophosphorylation of the COOH of the interaction of PDK-1 with protein kinase C phosphorylation site that PDK-1 preferentially unphosphorylated protein kinase C with Studies with reveal that the interaction is suggest that the conformation of unphosphorylated protein kinase C is for interaction with PDK-1, that at positions the The binding of phosphorylated is to from on the activation the unphosphorylated species of at the activation loop from phosphorylation of to with PDK-1 as unphosphorylated not This to the role of at the carboxyl terminus, and of in regulating the interaction of protein kinase C with PDK-1. Studies with constructs that the COOH terminus is a in the interaction of protein kinase C with PDK-1. Our data reveal two unphosphorylated is effectively with PDK-1 with phosphorylated protein kinase C, constructs of the carboxyl terminus are effective at disrupting the protein kinase interaction with both of is that phosphorylation of the carboxyl terminus of protein kinase C it to its conformation in a as to with the conformation of protein kinase C the affinity of phosphorylated protein kinase C for PDK-1. The that the COOH terminus is masked in the inactive conformation of protein kinase C is also by the finding that the of protein kinase C by of magnitude the active conformation Newton J. Biol. Chem. Full Text PDF PubMed Google Scholar). the interaction of PDK-1 with protein kinase C is regulated in by the phosphorylation state of the COOH terminus and the conformation of the protein the inactive conformation with the species of the tightly to PDK-1 than protein kinase, which a at constructs and phosphorylated carboxyl terminus of protein kinase an at the in the hydrophobic motif, constructs of protein kinase C with to effective than in binding PDK-1. binding at that an at the the of be to the not the of protein kinase C in the PDK-1 also the of phosphorylated protein kinase C in constructs not the interaction of protein kinase C with PDK-1, phosphorylation on the activation loop by for binding to protein kinase C, constructs the of protein kinase C. This suggests that of PDK-1 from protein kinase C the of protein kinase C by autophosphorylation. of from and A. A. M. A. Gaffney P. Downes C.P. D.R. Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar) also the hydrophobic phosphorylation as an in the regulation of PDK-1 a this a in the COOH terminus of the protein kinase kinase, that PDK-1 and it for PDK-1 A. A. M. A. Gaffney P. Downes C.P. D.R. Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). This the hydrophobic phosphorylation that the at the studies with constructs of that at the and the for of PDK-1. The that of in phosphorylation of and PDK-1 the the hydrophobic phosphorylation of The of this was that the interaction of PDK-1 with an in PDK-1 to activity and Our data an The binding of PDK-1 to protein kinase C, is regulated by autophosphorylation A. Newton J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). of effectively with binding PDK-1 a affinity for which a at the of the hydrophobic motif, than it does for the COOH terminus of of PDK-1 allow autophosphorylation. of and A. M. D.R. J. 2000; PubMed Scopus Google Scholar) that constructs of are phosphorylated at the activation loop not in the of the This is with data that phosphorylation of the intrinsic activity of this site is by autophosphorylation. the phosphorylation of is in from PDK-1 as be PDK-1 is the of the carboxyl terminus to the active site A. J. Cohen P. D.R. Curr. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). some activity activation loop constructs of with of at the activation loop activity Gaffney P.R. Reese C.B. Holmes A.B. Science. 1997; PubMed Scopus Google by with protein kinase C, the activity in the of from the of to PDK-1 from and the hydrophobic of to autophosphorylation. for the of the carboxyl terminus in PDK-1 to its from a which the COOH terminus of as a by PDK-1 A. M. D.R. J. 2000; PubMed Scopus Google Scholar). The COOH terminus of the turn phosphorylated in protein kinase C and at the the at the of the hydrophobic phosphorylation A. Newton J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). This the phosphorylated COOH terminus on the of the kinase by binding a hydrophobic on the of the D.R. J. Taylor S.S. Science. PubMed Scopus Google Scholar). in this are in PDK-1, and A. M. D.R. J. 2000; PubMed Scopus Google Scholar) to suggest that PDK-1, which does not a hydrophobic phosphorylation motif, an hydrophobic which and hydrophobic to this a that the COOH terminus of protein kinase an at its hydrophobic phosphorylation motif, is a site for PDK-1 A. M. D.R. J. 2000; PubMed Scopus Google Scholar). phosphorylation of the hydrophobic site on the S6 to a site for PDK-1 M. J. 2000; PubMed Scopus Google Scholar). The on a role for the hydrophobic in regulating the interaction of PDK-1 with its with the data in this to the following model for the interaction of PDK-1 with protein kinase C. PDK-1 associates with unphosphorylated protein kinase C. This interaction is the COOH terminus of protein kinase C, with the hydrophobic phosphorylation a role in the of PDK-1. PDK-1 protein kinase C βII on of the activation loop, the and in the of protein kinase C by phosphorylation A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar) PDK-1 from protein kinase C the carboxyl terminus and it for the autophosphorylation of and A. Newton Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). The phosphorylated COOH terminus its in a as to masked to PDK-1 PDK-1 a affinity for the COOH terminus it is phosphorylated with its affinity for the phosphorylated COOH terminus is in the of the protein kinase C. of the in conformational changes that the COOH terminus for binding to PDK-1. However, studies are to the role of protein kinase C activation in binding to PDK-1 in a cellular The release of PDK-1 from protein kinase C is by the of that contain at the hydrophobic as the phosphorylated carboxyl terminus of protein kinase C are phosphorylated hydrophobic that the interaction of PDK-1 with protein kinase C to be this a for phosphorylation at the COOH terminus of protein kinase C. is that the activated conformation of protein kinase C as a for PDK-1, this conformation an phosphorylated COOH terminus that is effective at binding PDK-1. this is the activation of protein kinase C be to the of protein kinase C. phosphorylated at the COOH terminus, phosphorylation of the activation loop on the activity of the in A. Newton Curr. Biol. 1998; 8: Full Text Full Text PDF PubMed Scopus Google Scholar). This suggests that the interaction of activated protein kinase C with PDK-1 is not to the function of protein kinase C. is to activation of protein kinase C in PDK-1 binding the of this interaction the COOH terminus as a in regulating the interaction of protein kinase C and vivo. Our data suggest that the carboxyl terminus of unphosphorylated protein kinase C PDK-1, with release of PDK-1 the carboxyl terminus to allow autophosphorylation. This release is by phosphorylated of the carboxyl terminus, which effectively for binding to PDK-1 the intrinsic affinity of PDK-1 for at the hydrophobic motif. This model not for promotes phosphorylation of the hydrophobic site of also in to a upstream kinase for protein kinase protein kinase an at its hydrophobic site and be to PDK-1 from protein kinase was in a protein M. Hemmings B.A. Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). The suggest two in the regulation of protein kinase C by 1) phosphorylation of the activation loop which is regulated by the activity of PDK-1, and 2) autophosphorylation of the the hydrophobic which is regulated by release of PDK-1 from protein kinase C. The of autophosphorylation to the activation loop phosphorylation by PDK-1 for the in the PDK-1 kinases this site (4Alessi D.R. James S.R. Downes C.P. Holmes A.B. Gaffney P.R. Reese C.B. Cohen P. Curr. Biol. 1997; 7: 261-269Abstract Full Text Full Text PDF PubMed Google Scholar, A. A. M. A. Gaffney P. Downes C.P. D.R. Curr. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, M. P. Hemmings B.A. Cell. Biol. PubMed Scopus Google Scholar).