>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=98.41 E-value=4.4e-06 Score=61.21 Aligned_cols=300 Identities=17% Similarity=0.230 Sum_probs=177.9 Q ss_pred CCCHHHHHHHHH-HHHHCCCCCCCEEECCCCCCHHHHHHHHHHHCCCCCCCCCCEEEEEECCCCCCCCCCCCCCCCCCCC Q ss_conf 689789999999-9972037864111026542025677776430013344332113432025665321123432233333 Q gi|254780488|r 80 YTHEPAEQLARL-LIKIAPLGLQYVFFSDSGSTSIEVALKMALGFFNNNNMPRNKIVVMEHGYHGDTIGSMSVSMRGAFN 158 (423) Q Consensus 80 ~~~~~~~~la~~-l~~~~p~~~~~v~f~~SGsEA~e~Alklar~~~~~~~~~r~~ii~~~~~yHG~t~~a~s~s~~~~~~ 158 (423) T Consensus 48 v~~PpI~~F~~daLA~Fl--G~D~~R~t~GARe~KfaVMhal--------C~~GD~vV~D~~AHYtsyvAAEra------ 111 (381) T TIGR02539 48 VTKPPIKDFLEDALAEFL--GMDVVRVTHGAREGKFAVMHAL--------CKEGDVVVLDGLAHYTSYVAAERA------ 111 (381) T ss_pred CCCCCHHHHHHHHHHHHH--CCCEEECCCCCCHHHHHHHHHH--------CCCCCEEEECCCCCHHHHHHHHHC------ T ss_conf 258831000455426672--7974540677502457887640--------899898998587454458999754------ Q ss_pred CCCCCCCCCCCCEE----CCC----CCCCCCCCCHHHHHCCCCCEEEEECCCCCCCCCCCCCCCCCCCCEEECCCCCCCC Q ss_conf 32223445421000----122----2222211110122127751134311655432112222333211001101112342 Q gi|254780488|r 159 NSYEPLLFDVETIP----FPH----HNEEQKTLDDLEKHCSTQKIAAFLVEPLILGAGGMQTYRPYILKEFMRITKKYDT 230 (423) Q Consensus 159 ~~~~p~~~~~~~i~----~~~----~~~~~~~l~~l~~~~~~~~iaavi~EP~i~~~gG~~~~~~~~l~~lr~lc~~~g~ 230 (423) T Consensus 112 -g-----l~v~eVPy~~g~P~Y~v~~e~Y~~viee~~d~~G~~-~~LallT-hvDG~YG-NL~DA---~kva~vc~~~gv 179 (381) T TIGR02539 112 -G-----LNVKEVPYETGHPEYKVDPEGYKEVIEEVEDESGKP-VALALLT-HVDGEYG-NLADA---KKVAKVCREKGV 179 (381) T ss_pred -C-----CEEEECCCCCCCCEEEECHHHHHHHHHHHHCCCCCC-CEEEEEE-ECCCCCC-CCHHH---HHHHHHHHHCCC T ss_conf -9-----727881655888607641667888886552027988-3489984-0268867-51124---568766542078 Q ss_pred EECCCCCCCCCCCCCCCCCCCCCCCCCCEEECC--CCCCCCCCCCCCCCCCHHHHHHHCCCCCCCCCCCCCCCC----CC Q ss_conf 000122124444555431122334444202013--443322234443322401321000122222222333332----22 Q gi|254780488|r 231 LLIADEVMTGWGRTGKIFACNHADITPDILCLS--KGITGGALPLAATLCSEEIFDSHLSSDKKKTFFHSSSYT----AN 304 (423) Q Consensus 231 llI~DEV~tG~GRtG~~~a~~~~gi~PDi~~~g--K~l~gG~~pisav~~~~~i~~~~~~~~~~~~~~h~~T~~----gn 304 (423) T Consensus 180 PlLLNCAY~-vGRm----Pv~~ke~~~DFiVGSGHKSMAAS-aP~GvLa~~eE~~~~v~r~Sslr-GdvsG~~~~~KEvE 252 (381) T TIGR02539 180 PLLLNCAYT-VGRM----PVSAKEIKADFIVGSGHKSMAAS-APCGVLAMSEEWEDKVLRKSSLR-GDVSGRKFPVKEVE 252 (381) T ss_pred CEEECCCCE-EEEE----CCCCCCCCCCEEEECCCCHHHHC-CCEEECCCCCCCCCCHHCCCCCC-CCCCCCCCCCCEEE T ss_conf 622124505-2100----31577778767780685132212-66002145422234011023210-03366344741277 Q ss_pred CCCHHHHHCCHH-HCCC-CCCCCCCC------CHHHHHHHHHHHHHHCCCEEEECCCCC----EEEEEECCCCC----CC Q ss_conf 210011000000-0001-12332221------002678989999751897777745533----99999706876----66 Q gi|254780488|r 305 PIACAAALANLQ-IWEK-EPVIERIK------NLERMHADRLSLLKSNKKFVNIRQMGT----IVALDFNVQNK----GY 368 (423) Q Consensus 305 pl~~aaa~a~L~-~i~~-~~l~~~~~------~~g~~l~~~l~~L~~~~~v~~vrG~Gl----~~~iel~~~~~----~~ 368 (423) T Consensus 253 lLGCT~rGap~~TlmASfP~VveRV~~Wd~Ev~ktRy~v~eLE~ig------G~~QlG~kPk~HDLv~FEtPgf~Eia~~ 326 (381) T TIGR02539 253 LLGCTSRGAPIVTLMASFPHVVERVKRWDEEVKKTRYFVAELEDIG------GFKQLGVKPKEHDLVKFETPGFHEIAKK 326 (381) T ss_pred ECCCCCCHHHHHHHHHCCCHHHHHCCCHHHHHHHHHHHHHHHHHCC------CEEECCCCCCCCCCEEECCCCCHHHHCC T ss_conf 4486324047999973281011220231566777657888764217------8886486888256414448840134144 Q ss_pred CCHHHHHHHHHHHHCCEEEEECC--CEEEECCCCCCCHHHHHHHHHHHHHHHHHH Q ss_conf 41068999999997885999519--989956898787999999999999999875 Q gi|254780488|r 369 FFDKNAKLKNFFREKKILIRPLG--HIMYLMPPYCITATDLDHIYNTINEAVDFL 421 (423) Q Consensus 369 ~~~~~~~l~~~l~~~Gil~~~~g--n~i~l~Ppl~it~~eId~~l~~l~~aL~~l 421 (423) T Consensus 327 ~kr~GyFLY~ELKkRgi~GI~~G~Tk~~K~Sv-YGL~~Eqv~~Vv~sf~eI~e~~ 380 (381) T TIGR02539 327 HKRRGYFLYEELKKRGIVGIRSGQTKEIKLSV-YGLTKEQVEYVVDSFKEIVEEY 380 (381) T ss_pred CCCCCCCHHHHHHHCCCEECCCCCCEEEEEEE-ECCCCCHHHHHHHHHHHHHHHC T ss_conf 87977640566531583001788742776433-1275211444467899999854

HHsearch alignment for GI: 254780488 and conserved domain: TIGR02539