>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=99.01 E-value=1.7e-08 Score=73.46 Aligned_cols=308 Identities=12% Similarity=0.067 Sum_probs=199.4 Q ss_pred HHHHHHHHHHHHHHHHHHCCCCCCEEEEECCCCHHHHHHHHHHCCCCCCEEEEEECCHHHHHHHHHHHCCCCCEEEEECC Q ss_conf 88999999999999999688998579997487348999875320578970799707368888876532387630674057 Q gi|254780153|r 44 VLGKERINKAIQLTRKVLEVPENYRIAIVPASDTGAVEMALWSLLGYRGVDVLAWESFGLGWMSDIRQLSLQDVREFTAP 123 (391) Q Consensus 44 ~~f~~i~~~~~~~l~~l~~~p~~y~v~~l~GsgT~~~ea~~~nl~~~~~~~~~~~g~~~~r~~~~~~~~~~~~~~~~~~~ 123 (391) T Consensus 51 PpI~~F~~d---aLA~FlG~-D---~~R~t~GARe~KfaVMhalC~~GD~vV~D~~AHYtsy--vAAEragl~v~eVPy~ 121 (381) T TIGR02539 51 PPIKDFLED---ALAEFLGM-D---VVRVTHGAREGKFAVMHALCKEGDVVVLDGLAHYTSY--VAAERAGLNVKEVPYE 121 (381) T ss_pred CCHHHHHHH---HHHHHHCC-C---EEECCCCCCHHHHHHHHHHCCCCCEEEECCCCCHHHH--HHHHHCCCEEEECCCC T ss_conf 831000455---42667279-7---4540677502457887640899898998587454458--9997549727881655 Q ss_pred CCC---CCC-------HHHCCC-----CCCEEEEEEECCCCEEECCEEE--ECCCCCCEEEEEECCHHHHCCCCCCC--C Q ss_conf 776---578-------676785-----5657997420242022032035--02568614886401101102545568--5 Q gi|254780153|r 124 YGS---LPD-------FSKVDF-----DRDVVFVWNGTTSGVCVPDVGF--IPESREGLVICDATSAVFARHIDFNK--L 184 (391) Q Consensus 124 ~g~---~~~-------~~~~~~-----~~~v~~~h~ETstGv~~~~~~~--~~~~~~~llivD~vSs~g~~p~d~~~--i 184 (391) T Consensus 122 ~g~P~Y~v~~e~Y~~viee~~d~~G~~~~LallThvDG~YGNL~DA~kva~vc~~~gvPlLLNCAY~vGRmPv~~ke~~~ 201 (381) T TIGR02539 122 TGHPEYKVDPEGYKEVIEEVEDESGKPVALALLTHVDGEYGNLADAKKVAKVCREKGVPLLLNCAYTVGRMPVSAKEIKA 201 (381) T ss_pred CCCCEEEECHHHHHHHHHHHHCCCCCCCEEEEEEECCCCCCCCHHHHHHHHHHHHCCCCEEECCCCEEEEECCCCCCCCC T ss_conf 88860764166788888655202798834899840268867511245687665420786221245052100315777787 Q ss_pred EEEEECCHHCCCCCCCCEEEEECHHHHHHHHHCC-CCCCCCCHHHCCHHHHHHCCCCCCCCC-CCCCHHHHHHHHHHHHH Q ss_conf 7999700120017665154456778887654114-457783123200112321033478644-66644889999999986 Q gi|254780153|r 185 DVVTFSAQKVLGGEAGFGIIILSPASVERLEKYV-PSWPLPKIFRMVKGGRVMEGLFCGETI-NTPSLLCIEDYIDALLW 262 (391) Q Consensus 185 Dv~~a~sQK~l~~ppGl~~v~~s~~al~~~~~~~-~~~~~~~~~~~~~~~~~~~~~~~~~~~-~TP~v~~i~al~~~l~~ 262 (391) T Consensus 202 DFiVGSGHKSMAASaP~GvLa~~eE~~~~v~r~SslrGdvs--G~~~~~-KEvE--lLGCT~rGap~~TlmASfP~VveR 276 (381) T TIGR02539 202 DFIVGSGHKSMAASAPCGVLAMSEEWEDKVLRKSSLRGDVS--GRKFPV-KEVE--LLGCTSRGAPIVTLMASFPHVVER 276 (381) T ss_pred CEEEECCCCHHHHCCCEEECCCCCCCCCCHHCCCCCCCCCC--CCCCCC-CEEE--ECCCCCCHHHHHHHHHCCCHHHHH T ss_conf 67780685132212660021454222340110232100336--634474-1277--448632404799997328101122 Q ss_pred HHCCCCHHHHHHHHHHHHHHHHHHHHHCCCCCCCCCCCCCCCCCEEEEEECCCCCCCCCHHHHHHHHHHHHHHHHHCCEE Q ss_conf 20103189999999977999999987479716766882003653178982473101137345678889999988862828 Q gi|254780153|r 263 LKKMGGLSACVERCNANAAVLFQFIQENDWIENLAVDETTRSNTSICMKIVDSDIASLDINSQKSFCKSMLSFLEKEEIA 342 (391) Q Consensus 263 i~~~gGl~~~~~r~~~~a~~l~~~i~~~~~~~~~~~~~~~rS~~~v~~~~~d~~~~~~~~~~~~~~~~~~~~~l~~~g~~ 342 (391) T Consensus 277 V~-------~Wd~Ev~ktRy~v~eLE~igG~~QlG~kPk~--H--DLv~FEtPgf~Eia~~~kr~Gy-FLY~ELKkRgi- 343 (381) T TIGR02539 277 VK-------RWDEEVKKTRYFVAELEDIGGFKQLGVKPKE--H--DLVKFETPGFHEIAKKHKRRGY-FLYEELKKRGI- 343 (381) T ss_pred CC-------CHHHHHHHHHHHHHHHHHCCCEEECCCCCCC--C--CCEEECCCCCHHHHCCCCCCCC-CHHHHHHHCCC- T ss_conf 02-------3156677765788876421788864868882--5--6414448840134144879776-40566531583- Q ss_pred ECCCCCCCCCCEEEEECCCCCCHHHHHHHHHHHHHHHHH Q ss_conf 726655676750568615888999999999999999999 Q gi|254780153|r 343 YDIGSYRDAPLGLRVWVGVTVEKEDLLLLCDWLRWVFYF 381 (391) Q Consensus 343 ~~~~~~r~~~~~~RIg~~g~i~~~dv~~L~~aLe~~~~~ 381 (391) T Consensus 344 ~GI~~G~T--k~~K~SvYG-L~~Eqv~~Vv~sf~eI~e~ 379 (381) T TIGR02539 344 VGIRSGQT--KEIKLSVYG-LTKEQVEYVVDSFKEIVEE 379 (381) T ss_pred EECCCCCC--EEEEEEEEC-CCCCHHHHHHHHHHHHHHH T ss_conf 00178874--277643312-7521144446789999985

HHsearch alignment for GI: 254780153 and conserved domain: TIGR02539