The Thermoplasma acidophilum LplA-LplB Complex Defines a New Class of Bipartite Lipoate-protein Ligases

Lipoic acid is a covalently bound cofactor found throughout the domains of life that is required for aerobic metabolism of 2-oxoacids and for C1 metabolism. Utilization of exogenous lipoate is catalyzed by a ligation reaction that proceeds via a lipoyl-adenylate intermediate to attach the cofactor to the ϵ-amino group of a conserved lysine residue of protein lipoyl domains. The lipoyl ligases of demonstrated function have a large N-terminal catalytic domain and a small C-terminal accessory domain. Half of the members of the LplA family detected in silico have only the large catalytic domain. Two x-ray structures of the Thermoplasma acidophilum LplA structure have been reported, although the protein was reported to lack ligase activity. McManus et al. (McManus, E., Luisi, B. F., and Perham, R. N. (2006) J. Mol. Biol. 356, 625–637) hypothesized that the product of an adjacent gene was also required for ligase activity. We have shown this to be the case and have named the second protein, LplB. We found that complementation of Escherichia coli strains lacking lipoate ligase with T. acidophilum LplA was possible only when LplB was also present. LplA had no detectable ligase activity in vitro in the absence of LplB. Moreover LplA and LplB were shown to interact and were purified as a heterodimer. LplB was required for lipoyl-adenylate formation but was not required for transfer of the lipoyl moiety of lipoyl-adenylate to acceptor proteins. Surveys of sequenced genomes show that most lipoyl ligases of the kingdom Archaea are heterodimeric. We propose that the presence of an accessory domain provides a diagnostic to distinguish lipoyl ligase homologues from other members of the lipoate/biotin attachment enzyme family. Lipoic acid is a covalently bound cofactor found throughout the domains of life that is required for aerobic metabolism of 2-oxoacids and for C1 metabolism. Utilization of exogenous lipoate is catalyzed by a ligation reaction that proceeds via a lipoyl-adenylate intermediate to attach the cofactor to the ϵ-amino group of a conserved lysine residue of protein lipoyl domains. The lipoyl ligases of demonstrated function have a large N-terminal catalytic domain and a small C-terminal accessory domain. Half of the members of the LplA family detected in silico have only the large catalytic domain. Two x-ray structures of the Thermoplasma acidophilum LplA structure have been reported, although the protein was reported to lack ligase activity. McManus et al. (McManus, E., Luisi, B. F., and Perham, R. N. (2006) J. Mol. Biol. 356, 625–637) hypothesized that the product of an adjacent gene was also required for ligase activity. We have shown this to be the case and have named the second protein, LplB. We found that complementation of Escherichia coli strains lacking lipoate ligase with T. acidophilum LplA was possible only when LplB was also present. LplA had no detectable ligase activity in vitro in the absence of LplB. Moreover LplA and LplB were shown to interact and were purified as a heterodimer. LplB was required for lipoyl-adenylate formation but was not required for transfer of the lipoyl moiety of lipoyl-adenylate to acceptor proteins. Surveys of sequenced genomes show that most lipoyl ligases of the kingdom Archaea are heterodimeric. We propose that the presence of an accessory domain provides a diagnostic to distinguish lipoyl ligase homologues from other members of the lipoate/biotin attachment enzyme family. Lipoic acid is a covalently bound cofactor that conveys activated reaction intermediates between different active sites of multienzyme complexes (1Perham R.N. Annu. Rev. Biochem. 2000; 69: 961-1004Crossref PubMed Scopus (468) Google Scholar). Lipoate is essential for aerobic metabolism of 2-oxoacids and for glycine cleavage. In its active form lipoate is attached to the ϵ-amino group of a small (∼80-residue) well conserved lipoyl domain (LD) 2The abbreviations used are: LDlipoyl domainCTDC-terminal domainNTAnitrilotriacetic acidE1E2, and E3, the three subunits of the 2-oxoacid complexes. 2The abbreviations used are: LDlipoyl domainCTDC-terminal domainNTAnitrilotriacetic acidE1E2, and E3, the three subunits of the 2-oxoacid complexes. lysine residue via an amide bond. LDs are typically found at the N termini of the E2 subunits of 2-oxoacid dehydrogenase complexes. In the 2-oxoacid complexes, lipoylated LD receives the decarboxylated acid from the E1 subunit active site in thioester linkage to a lipoate thiol. The acyl thioester is then converted to the corresponding CoA thioester by thioester exchange catalyzed by the E2 subunit active site. The dihydrolipoamide dehydrogenase subunit (E3) then oxidizes the dihydrolipoyl-LD back to the lipoyl-LD to reset the catalytic cycle. In the glycine cleavage (also called glycine decarboxylase and glycine dehydrogenase) system, the lipoyl domain exists as a free protein designated H. Lipoyl-LD receives the product of glycine decarboxylation, methylamine, from the P protein. The methylamine is then transferred to the T protein to produce methylenetetrahydrofolate that is typically used to synthesize serine from a second molecule of glycine. In Escherichia coli, lipoic acid is essential for aerobic growth because of the need for pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase. The glycine cleavage system is not required for growth of wild type E. coli strains but is required for growth of Arabidopsis where the H protein can be present at millimolar concentrations in photosynthetic cells (2Engel N. van den Daele K. Kolukisaoglu U. Morgenthal K. Weckwerth W. Pärnik T. Keerberg O. Bauwe H. Plant Physiol. 2007; 144: 1328-1335Crossref PubMed Scopus (108) Google Scholar). lipoyl domain C-terminal domain nitrilotriacetic acid E2, and E3, the three subunits of the 2-oxoacid complexes. lipoyl domain C-terminal domain nitrilotriacetic acid E2, and E3, the three subunits of the 2-oxoacid complexes. The reactions whereby lipoic acid-modified proteins are produced are best understood in E. coli. The most straightforward pathway is via lipoate-protein ligase, an activity first described by L. J. Reed et al. (3Reed L.J. Leach F.R. Koike M. J. Biol. Chem. 1958; 232: 123-142Abstract Full Text PDF PubMed Google Scholar) (see Fig. 1). These workers postulated that lipoate was attached to protein by a two-step ATP-dependent reaction with lipoyl-AMP as an activated intermediate (Fig. 1). Although the lipoate-protein ligases were key reagents in demonstration of the role of lipoic acid in the 2-oxoacid dehydrogenase reactions (3Reed L.J. Leach F.R. Koike M. J. Biol. Chem. 1958; 232: 123-142Abstract Full Text PDF PubMed Google Scholar, 4Koike M. Reed L.J. J. Biol. Chem. 1960; 235: 1931-1938Abstract Full Text PDF PubMed Google Scholar), the protein was not purified to homogeneity, and thus the proposed mechanism could not be considered proved. The E. coli lplA gene was the first gene encoding a lipoate-protein ligase isolated, and LplA was the first such ligase purified to homogeneity (5Green D.E. Morris T.W. Green J. Cronan Jr., J.E. Guest J.R. Biochem. J. 1995; 309: 853-862Crossref PubMed Scopus (93) Google Scholar, 6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar). The isolation of null mutants in lplA showed that LplA does not play a role in de novo lipoic acid synthesis but rather acts to scavenge lipoic acid from the environment (6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar, 7Morris T.W. Reed K.E. Cronan Jr., J.E. J. 1995; PubMed Scopus Google Scholar). LplA is a protein (5Green D.E. Morris T.W. Green J. Cronan Jr., J.E. Guest J.R. Biochem. J. 1995; 309: 853-862Crossref PubMed Scopus (93) Google Scholar). with a system have demonstrated that LplA lipoate and are to in vitro and that lipoyl-AMP is a reaction intermediate (5Green D.E. Morris T.W. Green J. Cronan Jr., J.E. Guest J.R. Biochem. J. 1995; 309: 853-862Crossref PubMed Scopus (93) Google Scholar, 6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar, R.N. J. PubMed Scopus Google Scholar, K. R.N. Biochem. J. PubMed Scopus Google Scholar). is that LplA the ATP-dependent of lipoate to lipoyl-AMP as well as the transfer of this activated lipoyl to with of The E. coli LplA enzyme been shown to be of lipoate and lipoate such as as for the of E2 in (5Green D.E. Morris T.W. Green J. Cronan Jr., J.E. Guest J.R. Biochem. J. 1995; 309: 853-862Crossref PubMed Scopus (93) Google Scholar, 6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar). structures of E. coli LplA and of LplA homologues have been reported an E. coli acid K. K. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar). The reported structures of the proteins well and show E. coli LplA to be a protein of a large N-terminal domain and a small C-terminal domain the E. coli acid is to because lipoic acid were bound to LplA the and were In case the lipoic acid was to in case was the K. K. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). show such and lipoic acid is a possible that the of the cofactor with a LplA in the was Moreover in K. E. Reed et al. K.E. Morris T.W. Cronan Jr., J.E. 1994; PubMed Scopus Google Scholar) had LplA mutants to by an of lipoic acid in the had been with this is a of the LplA the protein be to have an to the that the lipoic acid the site of this to serine T.W. Reed K.E. Cronan Jr., J.E. J. 1995; PubMed Scopus Google was from the lipoate site was by lipoic structures of an LplA from the Thermoplasma acidophilum J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar) that can be the E. coli LplA structure that the T. acidophilum protein the E. coli LplA C-terminal domain (Fig. In T. acidophilum structures the lipoate was adjacent to the glycine residue that to E. coli the residue to the and a of the molecule to of the was proposed E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar). Moreover of lipoic acid to a of the T. acidophilum LplA with lipoyl-AMP that the lipoic acid was bound in a J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The lipoyl-AMP was bound in a and was well from that the of the lipoate in the T. acidophilum LplA structures that lipoate sites the sites of E. coli LplA where lipoate was that the T. acidophilum LplA was in of the LplA reaction E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar). T. acidophilum LplA the C-terminal domain of E. coli LplA J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar), this that the domain was required for and a second protein was proposed to interact with T. acidophilum LplA to the reaction E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar). this were the the T. acidophilum lipoyl ligase an system to the role of the in lipoate-protein the lipoate-protein ligase reaction can be catalyzed by a protein this of lipoyl ligases from acyl In E. coli de novo lipoic acid is by the and the lipoyl J.E. Physiol. PubMed Scopus Google Scholar) (Fig. 1). the moiety from the protein intermediate of acid to the of the conserved LD lysine residue in (Fig. 1). then of a of and with from a via an mechanism J.E. Physiol. PubMed Scopus Google Scholar, J. Chem. PubMed Scopus Google Scholar). lipoic acid is its proteins J.R. Cronan J.E. Chem. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). Although the of LplA and show acid and different the proteins show and have active site J. PubMed Scopus Google Scholar, Cronan J.E. M. PubMed Scopus Google Scholar) (Fig. The and T. acidophilum LplA can be by with a of with of most Cronan J.E. M. PubMed Scopus Google Scholar). in and structure that lack the C-terminal domain. Although the E. coli and LplA a large of proteins in the have to and of a protein as a ligase is not an LplA can be a protein, an to distinguish lipoate ligases and be be that ligases also show not with and and this group of proteins the family J. J. K. PubMed Scopus Google Scholar). ligases have a C-terminal domain that in We as by McManus et al. E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar), the function essential for lipoate-protein ligase activity is by a gene of T. acidophilum lplA that and were as described J. in Scholar). were at T. acidophilum was from the were by and are shown in was and were with The was used for the and the was used for were sequenced by the J. of the of and used in this are in reagents and were from and were from and used in this T.W. Reed K.E. Cronan Jr., J.E. J. 1995; PubMed Scopus Google lplA T.W. Reed K.E. Cronan Jr., J.E. J. 1995; PubMed Scopus Google lplA lplA lplA lplA J.E. PubMed Scopus Google Biochem. 2000; PubMed Scopus Google with encoding a encoding N-terminal with with encoding encoding encoding E2 LD encoding the E2 encoding C-terminal encoding C-terminal encoding N-terminal encoding encoding in a E. coli strains were of E. coli was by the of and 2000; PubMed Scopus Google Scholar). The lplA gene was with a by of the product and The gene was with a the product and The were with the wild type the were the protein by the 2000; PubMed Scopus Google Scholar), and the lplA was growth with lipoic acid The strains are described in The and were as a by from T. acidophilum and and product was the sites of J.E. PubMed Scopus Google Scholar) the of an to was with and and and to by between the and site of to was with and and to by between the and sites of to of an N-terminal was from and also the N-terminal The product was to was and an a an N-terminal and an site. product was between the and sites of to The LD of the E2 subunit of the dehydrogenase was by to the LD by of pyruvate dehydrogenase E2 subunit R.N. Biochem. J. PubMed Scopus Google Scholar). The domain the first of the dehydrogenase E2 from The domain was from with and an site the and a was to The gene was then between the and sites of to T. acidophilum was found by and was with and a C-terminal and a site that the The product was to and the and sites of to was from with and and between the sites of to was from and the and sites of to and of domain homologues of LplB were the N. K. 2007; PubMed Scopus Google Scholar). homologues were the protein from of and and lipoic acid were the M. T. K. M. W. R. T. B. O. O. J. R. R. 2007; PubMed Scopus Google Scholar). were R. H. R. 2007; PubMed Scopus Google Scholar). and the ligase proteins were in with and lipoic The cells were at an of by and in at of were by a at were by at for of the pyruvate dehydrogenase and dehydrogenase were a of J. Biol. Chem. Full Text PDF PubMed Google Scholar, J.R. J. PubMed Scopus Google Scholar). The reaction and of pyruvate was also to activity. protein were the the The of from to by of at The of was at and the of the form in the was to be of of LplA and LplB was by exchange and were and the were at in of with and an of was with for and of the at were at The were in and and a The was at for and of a of was to the and for at with The was a and with at of and by The protein was with the The was in and to exchange a with a of an at protein, as by by were in that and The proteins were in and and at The of purified proteins were by The were to the of at for The E. coli domain was a from of this and had been purified by and exchange as described J.R. Cronan J.E. Chem. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). in cells was used to the E2 domain in with The was at an of for The was with and at of T. acidophilum E2 domain of the dehydrogenase was as described for E. coli domain J.R. Cronan J.E. Chem. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). exchange of the and of the domain as shown by domain was and as described for LplA and LplB. The of and were as described for LplA and LplB that was E2 domain were found to lack the N-terminal and were used to the glycine cleavage H protein in the LD in and the cells an of was as an and cells were by was purified by and exchange as described for LplA and LplB. concentrations were from the the The and The LplA and LplB were as different were were at for in the case of the T. acidophilum proteins and for the E. coli LD domain. domain was by by was by the of L. J. Reed et al. (3Reed L.J. Leach F.R. Koike M. J. Biol. Chem. 1958; 232: 123-142Abstract Full Text PDF PubMed Google Scholar). was and in as a for lipoyl domain by LplA and LplB. The reaction and LplA and LplB were as were at for domain was as described of lipoyl-AMP was The reactions and LplB and LplA were as The reaction was for at of the reaction was to a in had an of the of was The were and to a for to and a The reaction as was also with and was to this and for to of lipoyl-adenylate was the reaction with LplA and LplB a The reaction was with of to the and at for was by of the the protein was The were by and as described and were used to the and of the lipoyl ligase These strains have T. acidophilum lipoyl ligase proteins from a proteins were for in and in LplA and LplB were in cells with of and that a LplA and LplB. and that a LplB and The strains were in of with and where were to an of and was with for The cells were by and at was at in and used to cells at at for The was by at for The was then to a The was with of the were with of and were by was in a an at The was found to be were also to a The was from where is the is the and is the The of LplA to LplB was by protein with PubMed Scopus Google Scholar). was in with and were to an of was and cells were with were to with and and were to and of were to for by The cells were as The was purified a and the was to as described were to by The was and a and The of LplA to LplB was by the of the of The was for the of in protein for LplA and for E. coli lplA was used for complementation because the lack of lipoyl ligase no when lipoic acid is (6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar, 7Morris T.W. Reed K.E. Cronan Jr., J.E. J. 1995; PubMed Scopus Google Scholar). The lplA null of the E. coli was when lplA and of T. acidophilum were but not when the were was shown by of growth with lipoic acid (Fig. was to of 2-oxoacid complexes, an activity of a lipoyl ligase (Fig. in 2-oxoglutarate dehydrogenase activity was with LplA that the protein to lipoyl domains. was also by the complementation of growth by LplA (Fig. was because in vitro demonstrated no activity E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar) and that LplA of activity in the absence of LplB. The of 2-oxoglutarate dehydrogenase that T. acidophilum lipoyl ligase have a for this E2 domain does E. coli The ligation reaction was in LplA and LplB proteins were for the to the T. acidophilum E2 and LDs in the presence of lipoate and was only when LplA and LplB were present (Fig. Although as a activity was with LplA in detected no activity in vitro in with a E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar). was also a for as was demonstrated with E. coli lipoyl ligase (5Green D.E. Morris T.W. Green J. Cronan Jr., J.E. Guest J.R. Biochem. J. 1995; 309: 853-862Crossref PubMed Scopus (93) Google Scholar, 6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar). The E. coli LD was a but required LplB provides a for the function of the of the subunit lipoyl the reported synthesis of LplA J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) hypothesized that LplB be required for transfer of lipoate from lipoyl-AMP but not for this the of LplA and LplB with the lipoyl-adenylate intermediate were by by of formation (Fig. and by of lipoyl-adenylate as a (Fig. We found that lipoyl-adenylate was with as in the absence of LD The intermediate was from other by the system used for lipoyl-adenylate synthesis (3Reed L.J. Leach F.R. Koike M. J. Biol. Chem. 1958; 232: 123-142Abstract Full Text PDF PubMed Google Scholar) by and (Fig. of of the ligase was of a to that for E. coli ligase 1994; PubMed Scopus Google Scholar). The lipoyl-AMP intermediate with the ligase that the intermediate (Fig. We also to of the lipoyl-adenylate in lipoyl-AMP to of lipoyl-AMP by the PubMed Scopus Google Scholar). that no lipoyl-AMP bound to the LplB was required for formation (Fig. was with LplA in the presence of of and lipoic the that the active site the reaction was with domain with of not The were to and no lipoyl-adenylate was detected LplA and LplB were present. We also transfer of lipoate from lipoyl-AMP to an The (Fig. demonstrated that only the LplA protein was required for transfer of the lipoyl moiety and that LplB is not required for with the is not because the interact with LDs although lack a (Fig. Lipoic acid and were also the reaction because of the of the lipoyl-AMP with lipoyl-AMP could the domain PubMed Scopus Google Scholar). such was reaction (Fig. The was and LplA bound LplB (Fig. In LplB with LplA in no protein of the is to the of LplB and the of the LplB that be when LplB is with an that was the for an LplA and LplB when also such that a is a We have no for this but that was reported for of this protein E. coli K. PubMed Scopus Google Scholar). of the proteins with the of LplA to LplB to be LplA to LplB of was by the of LplA and the such that LplA present in the could have the LplA be because of from the of to In a second purified the by and the subunits by (Fig. of the a of LplA to LplB of that the is and with the that an was the best of the the of McManus et al. E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar) that LplB is the of the T. acidophilum Although LplB is the of the lipoate-protein ligase family is because is not of is a C-terminal domain. LplA homologues have a domain at N termini to a that are is a of the of the only domain that of T. acidophilum LplB. We this family be called the lipoyl ligase accessory domain family. We detected other domain LplB a LplB homologues are present in Archaea and but are not the lplA of are shown in Fig. Although the of sequenced Archaea is the gene to be the form of lipoyl are the lipoyl ligases of that that have and lack an are LplB homologues in with the that sequenced strains an LplB and a T. Although not lipoic a lipoyl ligase is found in the of the The of of with and accessory was proposed E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar). The of show that lipoyl-AMP formation the accessory domain. have only a catalytic domain but and protein that lipoyl ligase homologues lacking an accessory domain in the a different is the case for the lipoyl ligase have a that no with LplB (Fig. T. acidophilum are to but transfer the lipoyl moiety when lipoyl-AMP is K. H. M. K. M. H. J. Mol. Biol. 2007; PubMed Scopus Google Scholar). the of the function of the is not in We found that LplB and LplA are required for complementation of an lplA of E. coli and for of the pyruvate and 2-oxoglutarate In vitro and McManus et al. E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar) found that LplA to the lipoyl domain. et al. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) reported that first LplA in and then in lipoate the We were to lipoyl-AMP formation by LplA of a Moreover because LplA can lipoyl transfer from lipoyl-AMP to LD (Fig. and McManus et al. E. R.N. J. Mol. Biol. PubMed Scopus Google Scholar) have activity lipoyl-AMP had been The between the and of LplA be to lipoyl-AMP this were the case have in the lipoyl-AMP synthesis this was not the case (Fig. possible that the function of LplB is to the structure of LplA such that lipoyl-AMP synthesis can and that this the of the 2-oxoglutarate dehydrogenase in the presence of only LplA (Fig. that lipoyl-AMP is in could be to ligase activity by LplA by the presence of an E. coli that can LplB. The E. coli pyruvate dehydrogenase domains for the T. acidophilum of LplA LplA and LplB in E. coli in 2-oxoglutarate dehydrogenase activity pyruvate dehydrogenase although the enzyme three LDs E2 and a lipoylated LD is for activity (1Perham R.N. Annu. Rev. Biochem. 2000; 69: 961-1004Crossref PubMed Scopus (468) Google Scholar). the E. coli domain was a in vitro (Fig. The structures of lipoyl ligases a possible mechanism for LplB The structure of E. coli LplA that the conserved in residue the catalytic domain and is to the by conserved that the lipoyl-AMP K. K. H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The to acid is also present in this with its role in K.E. Morris T.W. Cronan Jr., J.E. 1994; PubMed Scopus Google Scholar). In an LplA structure the conserved of the accessory domain is also in to conserved residue and are to the conserved that the active site. structure of a active lipoyl ligase of activity with lipoyl-adenylate is not but an ligase structure been J. Mol. Biol. PubMed Scopus Google Scholar). Although LplB are conserved in the ligase accessory that the of the with the catalytic domain is The ligase accessory domain is and the that are present in the lipoyl ligase accessory domain. of been that members of the ligase to small and that activity J. Mol. Biol. PubMed Scopus Google Scholar). The role of the accessory domain in that be for of a small molecule the of ligase also been shown to be for Cronan Jr., J.E. PubMed Scopus Google Scholar). the lipoyl ligase family the lipoyl ligase accessory domain can be found as an N-terminal a as a protein is not found at (Fig. The accessory domains found as proteins are (Fig. the domain of lipoate ligases could be a The of a lipoyl ligase is not the accessory domain was and was of ligase is that the LplA protein family is in such (Fig. the T. acidophilum lipoyl ligase be an The activity of the T. acidophilum LplA and LplB with in of lipoate was first reported for the E. coli enzyme (6Morris T.W. Reed K.E. Cronan Jr., J.E. J. Biol. Chem. 1994; 269: 16091-16100Abstract Full Text PDF PubMed Google Scholar). in E. coli the can be converted to lipoyl-LD by lipoyl In T. acidophilum a lipoyl and thus the LD to function of its lipoic T. acidophilum need an environment in lipoic acid and in We and for in