Isolation and Characterization of T4 Bacteriophage gp17 Terminase, a Large Subunit Multimer with Enhanced ATPase Activity

Phage T4 terminase is a two-subunit enzyme that binds to the prohead portal protein and cuts and packages a headful of concatameric DNA. To characterize the T4 terminase large subunit, gp17 (70 kDa), gene 17 was cloned and expressed as a chitin-binding fusion protein. Following cleavage and release of gp17 from chitin, two additional column steps completed purification. The purification yielded (i) homogeneous soluble gp17 highly active inin vitro DNA packaging (∼10% efficiency, >108 phage/ml of extract); (ii) gp17 lacking endonuclease and contaminating protease activities; and (iii) a DNA-independent ATPase activity stimulated >100-fold by the terminase small subunit, gp16 (18 kDa), and modestly by portal gp20 and single-stranded binding protein gp32 multimers. Analyses revealed a preparation of highly active and slightly active gp17 forms, and the latter could be removed by immunoprecipitation using antiserum raised against a denatured form of the gp17 protein, leaving a terminase with the increased specific activity (∼400 ATPs/gp17 monomer/min) required for DNA packaging. Analysis of gp17 complexes separated from gp16 on glycerol gradients showed that a prolonged enhanced ATPase activity persisted after exposure to gp16, suggesting that constant interaction of the two proteins may not be required during packaging. Phage T4 terminase is a two-subunit enzyme that binds to the prohead portal protein and cuts and packages a headful of concatameric DNA. To characterize the T4 terminase large subunit, gp17 (70 kDa), gene 17 was cloned and expressed as a chitin-binding fusion protein. Following cleavage and release of gp17 from chitin, two additional column steps completed purification. The purification yielded (i) homogeneous soluble gp17 highly active inin vitro DNA packaging (∼10% efficiency, >108 phage/ml of extract); (ii) gp17 lacking endonuclease and contaminating protease activities; and (iii) a DNA-independent ATPase activity stimulated >100-fold by the terminase small subunit, gp16 (18 kDa), and modestly by portal gp20 and single-stranded binding protein gp32 multimers. Analyses revealed a preparation of highly active and slightly active gp17 forms, and the latter could be removed by immunoprecipitation using antiserum raised against a denatured form of the gp17 protein, leaving a terminase with the increased specific activity (∼400 ATPs/gp17 monomer/min) required for DNA packaging. Analysis of gp17 complexes separated from gp16 on glycerol gradients showed that a prolonged enhanced ATPase activity persisted after exposure to gp16, suggesting that constant interaction of the two proteins may not be required during packaging. Many dsDNA 1The abbreviations used are: dsDNA, double-stranded DNA; ssDNA, single-stranded DNA; CBD, chitin-binding domain; DTT, dithiothreitol; PEG, polyethylene glycol 1The abbreviations used are: dsDNA, double-stranded DNA; ssDNA, single-stranded DNA; CBD, chitin-binding domain; DTT, dithiothreitol; PEG, polyethylene glycolbacteriophage require the activity of two “terminase” proteins to cut and package concatameric DNA into assembled phage proheads. In T4, the gp16 (small subunit) and gp17 (large subunit) terminase proteins are essential proteins for DNA packaging. (Similar proteins are gpA and gpNu1 in λ phage, gp18 and gp19 in phage T7/T3, gp2 and gp3 in phage P22, and gp3 and gp16 in phage φ29.) As generally found among these phage terminases, the T4 small subunit confers the specific DNA-binding/association properties (1Wu C.H. Lin H. Black L.W. J. Mol. Biol. 1995; 247: 523-528PubMed Google Scholar, 2Wu C.H. Black L.W. J. Mol. Biol. 1995; 247: 604-617PubMed Google Scholar, 3Lin H. Simon M.N. Black L.W. J. Biol. Chem. 1997; 272: 3495-3501Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). The large subunit contains the prohead-binding and putative DNA-translocating ATPase activities (3Lin H. Simon M.N. Black L.W. J. Biol. Chem. 1997; 272: 3495-3501Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar, 4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar, 5Leffers G. Rao V.B. J. Biol. Chem. 2000; 275: 37127-37136Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, 6Rao V.B. Mitchell M.S. J. Mol. Biol. 2001; 314: 401-411Crossref PubMed Scopus (63) Google Scholar, 7Black L.W. Annu. Rev. Microbiol. 1989; 43: 267-292Crossref PubMed Scopus (364) Google Scholar). However, because the measured in vitro ATPase activities of isolated terminase proteins (8Rubinchik S. Parris W. Gold M. J. Biol. Chem. 1994; 269: 13586-13593Abstract Full Text PDF PubMed Google Scholar, 9Hamada K. Fujisawa H. Minagawa T. Virology. 1987; 159: 244-249Crossref PubMed Scopus (32) Google Scholar) have been low in comparison with measured rates of ATP consumption in packaging (10Guo P. Peterson C. Anderson D. J. Mol. Biol. 1987; 197: 229-236Crossref PubMed Scopus (227) Google Scholar,11Morita M. Tasaka M. Fujisawa H. Virology. 1993; 193: 748-752Crossref PubMed Scopus (83) Google Scholar), the identification of terminases as DNA-translocating ATPases has been problematic. What is clear is that packaging is ATP-driven and involves the cooperation of the DNA-associated terminase proteins with the prohead-associated portal vertex protein (7Black L.W. Annu. Rev. Microbiol. 1989; 43: 267-292Crossref PubMed Scopus (364) Google Scholar, 12Frackman S. Siegele D.A. Feiss M. J. Mol. Biol. 1984; 180: 283-300Crossref PubMed Scopus (61) Google Scholar, 13Bazinet C. King J. Annu. Rev. Microbiol. 1985; 39: 109-129Crossref PubMed Scopus (189) Google Scholar) in phage T4, gp20. The T4 terminase large subunit protein, gp17, has proven difficult to purify because of the protein's limited solubility and toxicity to host cells (14Bhattacharyya S.P. Rao V.B. Gene (Amst.). 1994; 146: 67-72Crossref PubMed Scopus (28) Google Scholar). Coexpression with the gp16 small subunit reduces toxicity; thus, gp17 could be purified with gp16 in low amounts from a temperature-induced expression vector (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar). A vector that makes gp17 with a 20-amino acid OmpT leader peptide results in low amounts of uninduced, soluble, and active protein, whereas the overexpressed protein is insoluble and inactive and resists renaturation (15Lin H. The Mechanism of the Phage T4 Terminase Complex, gp16 and gp17, in DNA Packaging.Ph.D. of of Scholar). A gp17 protein was overexpressed and showed in protein solubility as as acid to G. and W. G. and W. However, and Rao G. Rao V.B. J. Biol. Chem. 2000; 275: 37127-37136Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar) these by the and the expression from a cloned gp17 terminase is by to phage by in vitro DNA packaging and to and ATP (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar, 5Leffers G. Rao V.B. J. Biol. Chem. 2000; 275: 37127-37136Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar, L.W. Virology. PubMed Scopus Google Scholar), was ATPase and activities require interaction with additional acid protein To these and to highly purify gp17, column the of and to gp17 from The purified gp17 terminase ATPase activity is stimulated by with phage T4 proteins gp32 and gp20 with the terminase small subunit, that the enzyme preparation was of two of the protein, a form that could be by gp16 to a ATPase and a active form by immunoprecipitation with antiserum against denatured of low activity protein, ATPase activity of the activity for large subunit that of the two and that terminase a to form a activity is not interaction with The of terminase and that to the active and used as by the was as J. T. A Scholar). DNA using a and as T. J. A Scholar). by the using active gp17 was purified on the of To the gene 17 into vector a was and was for the of the gene and the of gene 17 was for the of the gene and the of gene 17 with a T4 DNA as for and a was with and was into vector vector was the and active gp17 was To protein a from was The gene 17 was isolated from vector and to vector was into and used to purification of active soluble gp17 for these the of of to A for with and with a of and ATP and the cells The cells two and for and the was removed and The was and a column in The column was with of column of and in and column of column of with was and the column was to in with with The showed that gp17 was from the column and to and in with The was large to of gp17, found to protein The protein was to a column and the of the gp17 protein was What to the column was in and and by and to a column in gp17 the column was with of and ATP a of The protein was from the column in of ATP and in and against of and and of the for enzyme The enzyme has been for these by protein by using a for of to protein was using T. J. A Scholar). of the purified gp17 protein and the to was from the and In was as D. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar). gp17 and gp16 proteins with of polyethylene glycol of the of ATPase to the The was DTT, and of and removed and as Rao V.B. Black L.W. J. Biol. Chem. Full Text PDF PubMed Google Scholar). DNA cleavage in using a that and polyethylene glycol of the terminase proteins of gp17 of in of and the by of of DNA. DNA and as and (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar), the gene and PubMed Scopus Google Scholar), a of P. for and for to and T. J. A Scholar). As in the of large protein J. H. J. D. J. Mol. Biol. 1995; 247: PubMed Scopus Google Scholar), in and with from to and the of the was and of the as in Scholar), of to the in from to gradients polyethylene by of glycerol in of glycerol in and the using a and and to to of could be and in for using a the of the to was as by in Scholar). was as a in and and to proteins in of from was and the was for of protein and the was for The was low and the was The was with for in a of and and a of the was The of raised against and active gp16 (3Lin H. Simon M.N. Black L.W. J. Biol. Chem. 1997; 272: 3495-3501Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar) and against the denatured form of OmpT terminase has been by Lin (15Lin H. The Mechanism of the Phage T4 Terminase Complex, gp16 and gp17, in DNA Packaging.Ph.D. of of Scholar), a of the proteins from D.A. PubMed Scopus Google Scholar). To purify the gp17 from the of antiserum was to in and a protein A column with of and of and in the column was with of A large of proteins was for was to the and in a was to with of was not for the gp17 ATPase from against and was to of using a The protein was to the terminase with a a of of gp16 with of and of gp17 and by and for of antiserum and the for of protein and for with the and the was removed for a small of the immunoprecipitation was the glycerol and from the of purified gp17 protein with of gp16 protein for of purified and the was for The was on of a glycerol and separated by for using the and using the and using of the gp17 terminase large subunit was on the fusion protein Gene 17 was cloned into the fusion vector to vector the In the fusion protein was soluble and in large amounts as by and using of fusion protein was after of with protein cells the gp17 fusion protein for and by and the the fusion protein was a column As proteins removed in the insoluble and not and in the of the column Many to with the fusion protein, could be removed after the column of the column in DTT, gp17 protein the of showed that the isolated protein could be from these using a solubility of gp17 from the column is homogeneous as by that gp17 in from the column was to and purification. In A the protein, was to The and the results of that A was the gp17 (70 and that the to from cleavage of gp17 two in of the gp17 by of acid of the found that gp17 not to (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar) and the of these removed not the contaminating in the preparation that with In after gp17 with and and showed that in to gp17 and that with exposure of purified from the gp17 not As a gp17 was to and with ATP and was not removed from the column of and ATP (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar). the protein was in and purification yielded of gp17 from of a The packaging of T4 DNA in vitro is the of the and of the terminase proteins (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar, L.W. Virology. PubMed Scopus Google Scholar, D. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar). In are with phage that to phage for terminase of terminase proteins vitro to these showed that phage be and that the gp17 protein is of phage, as of of purified terminase proteins enhanced activity The of purified gp17 protein in a using purified terminase proteins (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar), the of of phage that the and with G. Rao V.B. J. Biol. Chem. 2000; 275: 37127-37136Abstract Full Text Full Text PDF PubMed Scopus (82) Google vitro packaging of vitro packaging of the vitro packaging of the In vitro packaging of the in a to gp17 with T4 proteins with is to DNA in and have been with the gene as the of a (3Lin H. Simon M.N. Black L.W. J. Biol. Chem. 1997; 272: 3495-3501Abstract Full Text Full Text PDF PubMed Scopus (72) Google and have been by gp17 by gp17 with T4 proteins gp16, and In of was for the terminase proteins with with with the T4 gp17 and gp16 with DNA. gp17 was found to ATPase activity ATP that could be stimulated by of the gp16 small subunit terminase protein The gp16 protein was to ATPase activity (3Lin H. Simon M.N. Black L.W. J. Biol. Chem. 1997; 272: 3495-3501Abstract Full Text Full Text PDF PubMed Scopus (72) Google Scholar). gp17 to not the ATPase activity of the gp17 showed a of of the to the terminase proteins increased the activity by protein The purified terminase subunit and of to the T4 DNA cut with DNA and DNA DNA and DNA cut with and showed on the rates of ATP essential for the and The ATPase activity was The and on ATPase are in with the for vitro packaging by of these (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar). the of gp20 portal on the ATPase of gp17 A of portal purified gp20 J. Mol. Biol. PubMed Scopus Google Scholar), protein fusion The of and Terminase in the Mechanism of in the dsDNA of of Scholar), purified gp20 protein S. J. Mol. Biol. PubMed Scopus Google Scholar), and a peptide of gp20 to with gp17 H. Rao V.B. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar). gp20 protein fusion to ATPase rates not the gp20 preparation S. J. Mol. Biol. PubMed Scopus Google Scholar) showed of the gp20 peptide the ATPase interaction of gp17 with the T4 single-stranded binding protein gp32 has been S. J. Mol. Biol. PubMed Scopus Google Scholar), the of gp32 on the gp17 ATPase in the of acid of amounts of gp17 and amounts of gp16, of gp32 with increased the ATPase of the terminase of with gp32 increased the of ATP whereas T4 DNA with gp32 on the To the of gp16 on the gp17 ATPase with amounts of gp17 and ATP with amounts of gp16 of gp16 to gp17 to amounts increased the ATPase rates the ATPase rates in the amounts of gp16 in to on the ATPase of gp17 suggesting that the was to the on that gp16 have on gp17 these and a a for the of the of gp16 protein not the for gp16 binding to gp17 was to be binding of the two terminase with as as additional (4Rao V.B. Black L.W. J. Mol. Biol. 1988; 200: 475-488Crossref PubMed Scopus (102) Google Scholar, S. J. Mol. Biol. PubMed Scopus Google Scholar). To the with the gp17 ATPase binds the rates of ATP of ATP with of the terminase large of the gp16 small subunit and of gp16, the latter As the of ATP increased the rates of of the gp17 ATPase with amounts of gp16 a on the rates of ATP showed increased of and the to the of gp16 to the The of gp16 and of these showed that the of the gp16 to the ATPase was to of the and that the of the enzyme for ATP was not to the increased of gp16, as by the In to the gp17 ATPase with antiserum was with the gp17 protein and for on after of To in of antiserum increased the gp17 ATPase antiserum ATPase activity and not purified from antiserum stimulated the ATPase In the antiserum proteins of showed of the gp17 ATPase ATPase activities The enhanced gp17 ATPase activity in the of antiserum was of To the of on the gp17 ATPase a was to the used to the for The rates of ATP for gp17 with and for two of gp16 the of The of gp17 used for the was constant of to a of gp16 and a of gp16 not in additional in the ATP rates for the of the with the two gp16 was the in suggesting that raised the of gp16 to for in The of these showed in the of gp17 for ATP was not and that the of to gp16 was to of the with on for that the of gp17 ATPase from the interaction of with gp17 protein, that the with of the gp17 protein to with the of active gp17 in the on gp17 the latter because the of the ATPase activity could not be by of amounts of antiserum and protein gp17 and immunoprecipitation showed that of the gp17 ATPase activity in the after immunoprecipitation and that the ATPase showed on of gp16, not antiserum was was using to the gp16 protein after to gp17 on to the ATPase The results showed that the activity of gp16 was removed in and that gp17 activity in the after immunoprecipitation not suggesting that the two terminase proteins are essential for gp17 ATPase activity and W. on and Phage of Scholar). the the that binds the inactive gp17 protein and with the active of gp17 To the of the ATPase activity and gp17 protein in the and was The activity in the could be increased with amounts of whereas the of gp17 protein in the was the specific activity of the gp17 protein. In the of that could be used to of the gp17 of antiserum of gp17 was to a in the gp17 ATPase in the after As in A and ATPase activity was found in the after However, of the gp17 protein in the and showed that of amounts of antiserum increased the gp17, the gp17, and increased the ATPase of the gp17 in the and in was and the of these results are the In the active of the gp17, ATPase specific activity of of The results using antiserum purified from In active of gp17 protein. In to the of gp16 and gp17, was low J. H. J. D. J. Mol. Biol. 1995; 247: PubMed Scopus Google Scholar). interaction of the two proteins could be However, the of the gp17 protein on the showed low the purified protein as a with a of by in Scholar). and proteins and gp20 purified and in the yielded the in these not is that the portal and the terminase large subunit showed in kDa), the ATPase activity of gp17 the showed the highly active of the protein. As and for the interaction of gp16 and gp17 and to the of the active a for in small of purified gp17 on these gradients showed that the protein as as in comparison with protein not in to of gp17 with gp16 in of the gp17 protein the glycerol of with the of the protein the gp17 the gp16 and gp17 proteins not on the glycerol the in the of gp17 that of the gp17 protein with gp16 a on the gp17 protein's to and to form that the as in active of gp17 with inactive in the preparation to the active immunoprecipitation of the with removed a of low activity and low gp17, the showed that the activity gp17 as a in the of the glycerol Analysis of the gp17 protein showed a ATPase activity the activity in results with and that of the gp17 from the preparation the of a with To the that binds inactive gp17, gp17 with to the glycerol of the immunoprecipitation results showed that in the of gp17 the of the However, and ATPase of the showed that active gp17 protein the of the glycerol to the binding from of inactive gp17 protein. In to the gradients these of gp17 in the of showed that the gp17 protein was with ATPase specific activities found in to the of the the of the the of the the activity was these results the that two of the gp17 protein in and that the binds of the gp17 protein. with was found of in immunoprecipitation of active of the gp17 protein was to complexes with activity that the of the The that the the two is a because of the two that are separated by the ATPase by that gp17 with gp16 ATPase activity for the the of the gp17 with showed activity A as in that with gp16 in a in the gp17 protein, into form that persisted for a in the of The fusion protein of phage T4 terminase and the gp17 subunit in soluble and active form in a column found that terminase purification required two steps the of and proteins and to results in the protein, in the of protease ATPase and acid from the is to of the λ phage terminase large subunit, to a in the of protease and low W. S. Gold M. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar). W. S. Gold M. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar) found that the ATPase and activities in the protein and that the of the protein was the binding of the gpNu1 small subunit protein. The of the large subunit terminase proteins of and T4 phage to be essential for prohead portal interaction S. Siegele D.A. Feiss M. J. Mol. Biol. 1984; 180: 283-300Crossref PubMed Scopus (61) Google Scholar, M. Tasaka M. Fujisawa H. J. Mol. Biol. 1994; PubMed Scopus Google Scholar), the of gp17 is H. Rao V.B. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar). gp17 may protein in a lacking a binding of gp17 to to phage enzyme of a DNA cut enzyme the terminase large the specific packaging endonuclease (7Black L.W. Annu. Rev. Microbiol. 1989; 43: 267-292Crossref PubMed Scopus (364) Google Scholar), and is that the T4 terminase large subunit active gene in V.B. Mitchell M.S. J. Mol. Biol. 2001; 314: 401-411Crossref PubMed Scopus (63) Google Scholar, S.P. Rao V.B. Gene (Amst.). 1994; 146: 67-72Crossref PubMed Scopus (28) Google Scholar), to be to and terminase activities in preparation of that the gp17 terminase large subunit binds to the T4 is that the terminase is DNA interaction with proteins as and D. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar). gp17 was found to have low ATPase activity ATP proteins stimulated the gp16 terminase small subunit of gp32 binds gp17 S. J. Mol. Biol. PubMed Scopus Google Scholar), the ATP in the of The portal protein gp20 in the ATPase of gp17 ATPase that these proteins be because gp20 and gp32 is that interaction with the activity gp17 The purified gp17 ATPase activity could be stimulated >100-fold by of the gp16 terminase small subunit Analysis showed that the of the enzyme for ATP was not with gp16 the on the enzyme was to the of The for ATP was to be are in with and by and Rao G. Rao V.B. J. Biol. Chem. 2000; 275: 37127-37136Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar) and with ATPase rates in as λ phage, in vitro gpA ATPase has been (8Rubinchik S. Parris W. Gold M. J. Biol. Chem. 1994; 269: 13586-13593Abstract Full Text PDF PubMed Google Scholar, Feiss M. Virology. 1995; PubMed Scopus Google Scholar). The T4 terminase gp17 ATPase to be whereas the λ terminase gpA is DNA S. Parris W. Gold M. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar, Mol. 2000; PubMed Scopus Google Scholar). terminase proteins as of the and and have been ATPase activity in the of the and packaging (10Guo P. Peterson C. Anderson D. J. Mol. Biol. 1987; 197: 229-236Crossref PubMed Scopus (227) Google Scholar, K. Fujisawa H. Minagawa T. Virology. 1984; PubMed Scopus Google Scholar, 2001; PubMed Google Scholar). The T4 terminase gp17 activity is among large subunit terminase proteins in that has a activity stimulated by the of the small subunit could to the highly soluble and gp16 may to specific gp17 antiserum increased the ATPase of the gp17 protein by that the activity and the specific activity of the gp17 ATPase in the of the ATPase activity of gp17 in the in these showed that gp17 a of the activity for terminase and that the activity to for packaging of DNA. that DNA packaging rates in and λ of Feiss M. Virology. 1995; PubMed Scopus Google Scholar, H. Fujisawa H. Minagawa T. J. Mol. Biol. 1987; PubMed Scopus Google Scholar) and that ATP in and of (10Guo P. Peterson C. Anderson D. J. Mol. Biol. 1987; 197: 229-236Crossref PubMed Scopus (227) Google Scholar, H. Fujisawa H. Minagawa T. J. Mol. Biol. 1987; PubMed Scopus Google Scholar) to T4, a gp17 terminase of the required the additional ATPase by T4 proteins and In to the purified gp17 enzyme has a to form as has been for two and was on the found in the protein form a to be in because the protein ATPase activity the was difficult to the of A of preparation by showed that the preparation was of from a to with these glycerol of gp17 showed that the protein However, the highly active gp17 protein in the after immunoprecipitation as a large the of the with a of in comparison with Analysis showed that in the of gp17 complexes the by the low activity of the protein from of gp16 to gp17 in of the gp17 protein as a activity and suggesting that with gp16 to the to a highly active In was that antiserum of gp16 on gp17 ATPase ATPase showed that gp17 that was with gp16 ATPase activity the of the gp16 was on the exposure whereas gp17 that was not with gp16 not is the that the gp17 protein have enhanced ATPase activity in the of that with gp16 in a in the gp17 protein, into form that persisted for a in the of the and low activity gp17 proteins is with by The that the highly active gp17 ATPase interaction with gp17 to the gp17 in the active to be because form is not and because is found to gp17 in the highly active form in and A and not be The that terminase large is not a (10Guo P. Peterson C. Anderson D. J. Mol. Biol. 1987; 197: 229-236Crossref PubMed Scopus (227) Google Scholar, H. Rao V.B. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar, Feiss M. Virology. 1995; PubMed Scopus Google Scholar, S. Parris W. Gold M. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar, H. H. H. Virology. PubMed Scopus Google Scholar). is the that gp17 and large subunit terminase proteins may to a of proteins Mol. Biol. 2001; PubMed Scopus (61) Google Scholar, J. Mol. Biol. PubMed Scopus Google Scholar). of the properties of gp17 that for in thus, gp17 is in a of phage with gp16, and D. Black L.W. J. Mol. Biol. PubMed Scopus Google Scholar) and DNA; binds and is highly to and in The gp16 small subunit interaction is for to a highly active and protein may be to the protein into specific for packaging. and for the for for