>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=98.91 E-value=4.6e-08 Score=76.64 Aligned_cols=329 Identities=17% Similarity=0.264 Sum_probs=214.7 Q ss_pred HHHCCCCCCCC--CCCCHHHHHHHHCCCCCCCCCCCCCCCCCCCCHHHHHHHHHHHH----H-HHHHCCCCCEECCCHHH Q ss_conf 98388810430--10298999983051028865798887533600679999999999----9-99871886301000016 Q gi|254780349|r 32 QNDEIQLIASE--NIVSRAVLEAQGSILTNKYAEGYPSKRYYGGCQYVDDIENIAIE----R-AKKLFNVNFVNVQSHSG 104 (433) Q Consensus 32 q~~~l~LiASE--N~~S~~v~~~l~S~l~nkyaeG~pg~ryy~G~~~~d~iE~la~~----~-a~~lF~a~~anvqp~SG 104 (433) T Consensus 5 ~r~~iN~nPlQrGGvLt~~ArkAl-~EfGDGYSV----CDfC~G--~Ld~v~~PpI~~F~~daLA~FlG~D~--~R~t~G 75 (381) T TIGR02539 5 EREFINLNPLQRGGVLTEAARKAL-VEFGDGYSV----CDFCEG--RLDEVTKPPIKDFLEDALAEFLGMDV--VRVTHG 75 (381) T ss_pred CCCCCCCCCCCCCCCCHHHHHHHE-EEECCCCEE----EECCCC--EECCCCCCCHHHHHHHHHHHHHCCCE--EECCCC T ss_conf 121316784346887837787100-422685238----530387--70352588310004554266727974--540677 Q ss_pred HH-HHHHHHHHHHCCCCEEEECCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCHHHHHHHHHHH------CCCEE Q ss_conf 79-999999983154874881233448411147665433333220136658323565989999999860------46678 Q gi|254780349|r 105 SQ-MNQGVFLALMHPGDSFMGLSLDSGGHLTHGSSVNMSGKWFKAIPYNVRKEDGLLDMHEIESLAIEY------NPKLI 177 (433) Q Consensus 105 ~~-An~av~~ALl~pGD~Il~~~l~~GGHlshg~~~~~~g~~~~~~~y~~d~~~~~ID~d~~~~~a~~~------kPklI 177 (433) T Consensus 76 ARe~KfaVMhalC~~GD~vV~D~~---AHYtsyvAAEragl~v~eVPy~~g~P~Y~v~~e~Y~~viee~~d~~G~~~~La 152 (381) T TIGR02539 76 AREGKFAVMHALCKEGDVVVLDGL---AHYTSYVAAERAGLNVKEVPYETGHPEYKVDPEGYKEVIEEVEDESGKPVALA 152 (381) T ss_pred CCHHHHHHHHHHCCCCCEEEECCC---CCHHHHHHHHHCCCEEEECCCCCCCCEEEECHHHHHHHHHHHHCCCCCCCEEE T ss_conf 502457887640899898998587---45445899975497278816558886076416678888865520279883489 Q ss_pred EEEC--CCCCCCCCHHHHHHHHHHCCCEEEECCCCHHHHHHHHCCCCCCCC--CCEEEECCCCCCC--CCCCEEEEECCC Q ss_conf 9705--524353637999988641797899186201244320001232200--2356740456522--567448983362 Q gi|254780349|r 178 IVGG--TAYSRVWDWERFRSIADSIGAYLMADISHISGLVVGGQHPSPVPH--CHIVTTTTHKSLR--GPRGGLIMTNHA 251 (433) Q Consensus 178 i~G~--S~y~~~~d~~~l~eIa~~~ga~l~~D~aH~~GLIa~g~~~~Pl~~--ADvvt~sTHKtl~--GPrgGiI~~~~~ 251 (433) T Consensus 153 llThvDG~YGNL~DA~kva~vc~~~gvPlLLNCAY~vG-----RmPv~~ke~~~DFiVGSGHKSMAASaP~G-vLa~~-e 225 (381) T TIGR02539 153 LLTHVDGEYGNLADAKKVAKVCREKGVPLLLNCAYTVG-----RMPVSAKEIKADFIVGSGHKSMAASAPCG-VLAMS-E 225 (381) T ss_pred EEEECCCCCCCCHHHHHHHHHHHHCCCCEEECCCCEEE-----EECCCCCCCCCCEEEECCCCHHHHCCCEE-ECCCC-C T ss_conf 98402688675112456876654207862212450521-----00315777787677806851322126600-21454-2 Q ss_pred CHHHHCCH-HHCHHHHHHH-HHH--------HHHHHHHHHHHHHCHHHHHH---HHHHHHHHHHHHHHHHHCC-CCCCCC Q ss_conf 05650166-4654322344-556--------66899999999735648999---9999988899999986168-523345 Q gi|254780349|r 252 DLAKKINS-AIFPGLQGGP-FMH--------SIAAKAVAFGEALSSEFRDY---AKQIVLNSQALAKKLQFLG-FDIVSG 317 (433) Q Consensus 252 e~~~~i~~-avfPg~qg~~-~~~--------~iaa~aval~Ea~~~~f~~Y---a~qvv~NA~~La~~L~~~G-~~vv~g 317 (433) T Consensus 226 E~~~~v~r~SslrGdvsG~~~~~KEvElLGCT~rGap~~TlmASfP~VveRV~~Wd~Ev~ktRy~v~eLE~igG~~QlG~ 305 (381) T TIGR02539 226 EWEDKVLRKSSLRGDVSGRKFPVKEVELLGCTSRGAPIVTLMASFPHVVERVKRWDEEVKKTRYFVAELEDIGGFKQLGV 305 (381) T ss_pred CCCCCHHCCCCCCCCCCCCCCCCCEEEECCCCCCHHHHHHHHHCCCHHHHHCCCHHHHHHHHHHHHHHHHHCCCEEECCC T ss_conf 22340110232100336634474127744863240479999732810112202315667776578887642178886486 Q ss_pred CCCCCEEEECCCCCCC---------CHHHHHHHHHHCCEEEECCCCCCCCCCCCCCCCCCCCCHH---HHHCCCCHHHHH Q ss_conf 8889812631665567---------6799999888567188037899899998889851224666---730799989999 Q gi|254780349|r 318 GTDNHLMLVDLRSKRM---------TGKRAESILGRVSITCNKNSIPFDPESPFITSGIRLGTPS---GTTRGFKEKDFE 385 (433) Q Consensus 318 gTd~H~vlvdl~~~~~---------~G~~a~~~Le~~gI~~Nkn~iP~D~~~~~~~sGiRlGT~a---iTtrG~~e~em~ 385 (433) T Consensus 306 kPk~HDLv~-FEtPgf~Eia~~~kr~GyFLY~ELKkRgi-----------------~GI~~G~Tk~~K~SvYGL~~Eqv~ 367 (381) T TIGR02539 306 KPKEHDLVK-FETPGFHEIAKKHKRRGYFLYEELKKRGI-----------------VGIRSGQTKEIKLSVYGLTKEQVE 367 (381) T ss_pred CCCCCCCEE-ECCCCCHHHHCCCCCCCCCHHHHHHHCCC-----------------EECCCCCCEEEEEEEECCCCCHHH T ss_conf 888256414-44884013414487977640566531583-----------------001788742776433127521144 Q ss_pred HHHHHHHHHHHC Q ss_conf 999999999602 Q gi|254780349|r 386 YIGELIAQILDG 397 (433) Q Consensus 386 ~iA~li~~~L~~ 397 (433) T Consensus 368 ~Vv~sf~eI~e~ 379 (381) T TIGR02539 368 YVVDSFKEIVEE 379 (381) T ss_pred HHHHHHHHHHHH T ss_conf 446789999985

HHsearch alignment for GI: 254780349 and conserved domain: TIGR02539