>TIGR02539 SepCysS Sep-tRNA:Cys-tRNA synthase; InterPro: IPR013375 The aminoacyl-tRNA synthetases (6.1.1. from EC) catalyse the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction. These proteins differ widely in size and oligomeric state, and have limited sequence homology . The 20 aminoacyl-tRNA synthetases are divided into two classes, I and II. Class I aminoacyl-tRNA synthetases contain a characteristic Rossman fold catalytic domain and are mostly monomeric . Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices , and are mostly dimeric or multimeric, containing at least three conserved regions , , . However, tRNA binding involves an alpha-helical structure that is conserved between class I and class II synthetases. In reactions catalysed by the class I aminoacyl-tRNA synthetases, the aminoacyl group is coupled to the 2'-hydroxyl of the tRNA, while, in class II reactions, the 3'-hydroxyl site is preferred. The synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan and valine belong to class I synthetases; these synthetases are further divided into three subclasses, a, b and c, according to sequence homology. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, lysine, phenylalanine, proline, serine, and threonine belong to class-II synthetases . Many archaeal species lack cysteinyl-tRNA synthetase, an essential enzyme that provides Cys-tRNA(Cys) in other organisms. Instead, in a two step pathway, tRNA-Cys is acylated with O-phosphoserine (Sep) to form Sep-tRNA(Cys), which is subsequently converted to Cys-tRNA(Cys) . This pathway is also thought to function as the sole route of cysteine biosynthesis in these organisms. Several other archaeal species use both this pathway and direct tRNA(Cys) aminoacylation to synthesize Cys-tRNA(Cys), but this pathway appears to be the only route for cysteine biosynthesis. Proteins in this entry catalyse the second step in this pathway using pyridoxal phosphate and a sulphur donor to synthesize Cys from Sep while attached to the tRNA..

Probab=99.86 E-value=7.7e-21 Score=153.96 Aligned_cols=326 Identities=16% Similarity=0.164 Sum_probs=233.5 Q ss_pred EEEEEECCCCCCCCCCCHHHHHHHHHHHHHHCCC-----CCCCHHCCCCCCHHHH-HHHHHHHHCCCCCEEEEECCCCCH Q ss_conf 6899811447466779889999999999982987-----7641000276402899-999888734997337740565201 Q gi|254780604|r 45 RKVTIWCSNDYLGMGKHPKVIENAQRTFEKCGIG-----AGGTRNIAGTNYYHVM-LEKELATLHGKKAALIFNSGYIAN 118 (401) Q Consensus 45 ~~~l~f~sndYLgL~~~p~v~~a~~~a~~~~G~~-----~~~sr~~~G~~~~~~~-LE~~la~~~g~e~al~~~SG~~An 118 (401) T Consensus 6 r~~iN~nP-----lQrGGvLt~~ArkAl~EfGDGYSVCDfC~G~Ld~v~~PpI~~F~~daLA~FlG~D~~R~t~GARe~K 80 (381) T TIGR02539 6 REFINLNP-----LQRGGVLTEAARKALVEFGDGYSVCDFCEGRLDEVTKPPIKDFLEDALAEFLGMDVVRVTHGAREGK 80 (381) T ss_pred CCCCCCCC-----CCCCCCCHHHHHHHEEEECCCCEEEECCCCEECCCCCCCHHHHHHHHHHHHHCCCEEECCCCCCHHH T ss_conf 21316784-----3468878377871004226852385303877035258831000455426672797454067750245 Q ss_pred HHHHCCCCCCCCCEEEEHHHHHHHHHHHHHHHCCCCEEEEC-C-------CCHHHHHHHHHHCCCC---CCCEEE---CC Q ss_conf 22202346778872342132111675201453165135316-7-------9988988867406633---562362---16 Q gi|254780604|r 119 WATIGTLCSQIDNIICFSDSHNHASIIEGINKARCKKVIWN-H-------NDLEDLEKNLAATDLS---IPKIII---FE 184 (401) Q Consensus 119 ~~~i~~l~~~~d~ii~~~D~~~HaSi~~g~~l~~a~~~~f~-H-------nD~~~Le~~L~~~~~~---~~~iIv---~e 184 (401) T Consensus 81 faVMhalC~~GD~vV~--D~~AHYtsyvAAEragl~v~eVPy~~g~P~Y~v~~e~Y~~viee~~d~~G~~~~LallThvD 158 (381) T TIGR02539 81 FAVMHALCKEGDVVVL--DGLAHYTSYVAAERAGLNVKEVPYETGHPEYKVDPEGYKEVIEEVEDESGKPVALALLTHVD 158 (381) T ss_pred HHHHHHHCCCCCEEEE--CCCCCHHHHHHHHHCCCEEEECCCCCCCCEEEECHHHHHHHHHHHHCCCCCCCEEEEEEECC T ss_conf 7887640899898998--58745445899975497278816558886076416678888865520279883489984026 Q ss_pred CCCCCCCCHHHHHHHHHHHHCCCCEEEECCCCCCCCCCCHHHHHHHHHHCCCCCCHHHCCCCCCCCCCE--EEEECCHHH Q ss_conf 743567733689999998401471899712110012560258999997202001011014443222231--687548445 Q gi|254780604|r 185 SIYSMDGDIAPIKEICDLADQYNAITYIDEVHAVGIHGSCGAGISEREGIMNRITIISGTLAKGFGTFG--GYIAASENL 262 (401) Q Consensus 185 ~v~Sm~G~~apL~~l~~l~~~~~~~LivDEAH~~Gv~G~~G~G~~~~~g~~~~~di~~~TlsKa~g~~G--G~i~g~~~~ 262 (401) T Consensus 159 G~Y---GNL~DA~kva~vc~~~gvPlLLNCAY~vGRm--------Pv~~ke~~~DFiVGSGHKSMAASaP~GvLa~~eE~ 227 (381) T TIGR02539 159 GEY---GNLADAKKVAKVCREKGVPLLLNCAYTVGRM--------PVSAKEIKADFIVGSGHKSMAASAPCGVLAMSEEW 227 (381) T ss_pred CCC---CCCHHHHHHHHHHHHCCCCEEECCCCEEEEE--------CCCCCCCCCCEEEECCCCHHHHCCCEEECCCCCCC T ss_conf 886---7511245687665420786221245052100--------31577778767780685132212660021454222 Q ss_pred HHHHHCCC--CC-------------CCCCCCCCCHHHHHHHHHHHHHHCCHHHHHHHHHHHHHHHHHHHHCC-CCCCCC- Q ss_conf 00000133--22-------------23334444314788998764320120168888999987666566449-830378- Q gi|254780604|r 263 CDFIRSFA--SG-------------FIFSTSLPPAIASASVTSIQYIKQHYDERKKYLERVKQLRHSLENKA-IPCIPN- 325 (401) Q Consensus 263 ~~~l~~~~--~~-------------~ifs~~l~p~~~aa~~~al~~l~~~~~~~~~l~~~~~~l~~~L~~~g-~~~~~~- 325 (401) T Consensus 228 ~~~v~r~SslrGdvsG~~~~~KEvElLGCT~rG-ap~~TlmASfP~VveRV~~Wd~Ev~ktRy~v~eLE~igG~~QlG~k 306 (381) T TIGR02539 228 EDKVLRKSSLRGDVSGRKFPVKEVELLGCTSRG-APIVTLMASFPHVVERVKRWDEEVKKTRYFVAELEDIGGFKQLGVK 306 (381) T ss_pred CCCHHCCCCCCCCCCCCCCCCCEEEECCCCCCH-HHHHHHHHCCCHHHHHCCCHHHHHHHHHHHHHHHHHCCCEEECCCC T ss_conf 340110232100336634474127744863240-4799997328101122023156677765788876421788864868 Q ss_pred ---------CCCEEEEEECC-HHHHHHHHHHHHHHCCEEEEEECCCCCCCCCCEEEEECCCCCCHHHHHHHHHHHHHHHH Q ss_conf ---------98659999689-79999999999973790998404888888872189961857999999999999999999 Q gi|254780604|r 326 ---------ESHIIPIMVGD-SHKCTQISNILLKEFGIYIQPINYPTVAKKKERLRVTLTPLHTDSDIEHLVSSLENVWQ 395 (401) Q Consensus 326 ---------~s~Ivpi~~g~-~~~~~~~~~~lL~e~Gi~v~~i~~PtVp~g~~rlRi~l~a~ht~edid~~~~~l~~v~~ 395 (401) T Consensus 307 Pk~HDLv~FEtPgf~Eia~~~kr~GyFLY~E-LKkRgi~--GI~~G----~Tk~~K~SvY-GL~~Eqv~~Vv~sf~eI~e 378 (381) T TIGR02539 307 PKEHDLVKFETPGFHEIAKKHKRRGYFLYEE-LKKRGIV--GIRSG----QTKEIKLSVY-GLTKEQVEYVVDSFKEIVE 378 (381) T ss_pred CCCCCCEEECCCCCHHHHCCCCCCCCCHHHH-HHHCCCE--ECCCC----CCEEEEEEEE-CCCCCHHHHHHHHHHHHHH T ss_conf 8825641444884013414487977640566-5315830--01788----7427764331-2752114444678999998 Q ss_pred HH Q ss_conf 74 Q gi|254780604|r 396 KM 397 (401) Q Consensus 396 ~l 397 (401) T Consensus 379 ~~ 380 (381) T TIGR02539 379 EY 380 (381) T ss_pred HC T ss_conf 54

HHsearch alignment for GI: 254780604 and conserved domain: TIGR02539