>TIGR00392 ileS isoleucyl-tRNA synthetase; InterPro: IPR002301 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 . Isoleucyl-tRNA synthetase (6.1.1.5 from EC) is an alpha monomer that belongs to class Ia. The enzyme, isoleucyl-transfer RNA synthetase, activates not only the cognate substrate L-isoleucine but also the minimally distinct L-valine in the first, aminoacylation step. Then, in a second, "editing" step, the synthetase itself rapidly hydrolyzes only the valylated products , as shown from the crystal structures. ; GO: 0000166 nucleotide binding, 0004822 isoleucine-tRNA ligase activity, 0005524 ATP binding, 0006412 translation, 0006428 isoleucyl-tRNA aminoacylation, 0005737 cytoplasm.

Probab=95.33  E-value=0.012  Score=37.81  Aligned_cols=84  Identities=20%  Similarity=0.297  Sum_probs=48.2

Q ss_pred             HHHHHHHCCHHHHHHHHHHHCCCCEEHHHHHHHHHHHHHHHHHHHHHHHCHHHHHH--CCCCCCCCCCCCCCCCCCCCCC
Q ss_conf             13466411114665435652866011121212689999999999987614011000--0012321113457431432234
Q gi|254780794|r  125 TASLGLFMYPVLMAADILLYRATHVPVGEDQRQHLEITRLIAQRFNTEFERKIKEV--AQKYAQEEQYSKGFFPIIEGLI  202 (355)
Q Consensus       125 ~~~~g~~~YP~lqaADIl~~~a~~VpVG~DQ~~HieltRdiA~rfN~~yg~~~~~~--~~~~~~~~~~~~~~~~~p~~~i  202 (355)
T Consensus       600 s~~~A~~~~~~~~~~~~~~~pAD~i~EG~DQ~------RGW---FySsl~~~~~~~nv~~~PYK~V--------i~hGF-  661 (938)
T TIGR00392       600 SMPYAVLHYPFENEKFKEVFPADFILEGSDQT------RGW---FYSSLLIGVALFNVGKAPYKNV--------ITHGF-  661 (938)
T ss_pred             HHHHHHHHCCCCCHHHCCCCCCEEEEECCCCC------CHH---HHHHHHHHHHHHCCCCCCCCEE--------EECCE-
T ss_conf             11799863232100103578302686033555------327---7999999999870788543634--------53154-


Q ss_pred             CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCHHHHHH
Q ss_conf             756430335677411132134554452001453889999
Q gi|254780794|r  203 DSSASRIRSLRDASKKMSKSDSSDFSRINLLDNPDIIAK  241 (355)
Q Consensus       203 ~~~~~ri~~L~~~~~KMSKS~~~~~s~I~l~D~~e~I~k  241 (355)
T Consensus       662 --------~LDe~G~KMSKSlG---NvV~----P~~v~~  685 (938)
T TIGR00392       662 --------TLDEKGRKMSKSLG---NVVD----PEKVIN  685 (938)
T ss_pred             --------EECCCCCCCCCCCC---CCCC----HHHHCC
T ss_conf             --------88577854453258---7038----599708