Queuine tRNA-ribosyltransferase catalytic subunit 1 (EC 2.4.2.64) (Guanine insertion enzyme) (tRNA-guanine transglycosylase)
1_MAGAA 6_ TQASL 11_ ESAPR 16_ IMRLV 21_ AECSR 26_ SRARA 31_ GELWL 36_ PHGTV 41_ ATPVF 46_ MPVGT 51_ QATMK 56_ GITTE 61_ QLDAL 66_ GCRIC 71_ LGNTY 76_ HLGLR 81_ PGPEL 86_ IQKAN 91_ GLHGF 96_ MNWPH 101_ NLLTD 106_ SGGFQ 111_ MVSLV 116_ SLSEV 121_ TEEGV 126_ RFRSP 131_ YDGNE 136_ TLLSP 141_ EKSVQ 146_ IQNAL 151_ GSDII 156_ MQLDD 161_ VVSST 166_ VTGPR 171_ VEEAM 176_ YRSIR 181_ WLDRC 186_ IAAHQ 191_ RPDKQ 196_ NLFAI 201_ IQGGL 206_ DADLR 211_ ATCLE 216_ EMTKR 221_ DVPGF 226_ AIGGL 231_ SGGES 236_ KSQFW 241_ RMVAL 246_ STSRL 251_ PKDKP 256_ RYLMG 261_ VGYAT 266_ DLVVC 271_ VALGC 276_ DMFDC 281_ VFPTR 286_ TARFG 291_ SALVP 296_ TGNLQ 301_ LRKKV 306_ FEKDF 311_ GPIDP 316_ ECTCP 321_ TCQKH 326_ SRAFL 331_ HALLH 336_ SDNTA 341_ ALHHL 346_ TVHNI 351_ AYQLQ 356_ LMSAV 361_ RTSIV 366_ EKRFP 371_ DFVRD 376_ FMGAM 381_ YGDPT 386_ LCPTW 391_ ATDAL 396_ASVGI
1: Catalytic subunit of the queuine tRNA-ribosyltransferase (TGT) that catalyzes the base-exchange of a guanine (G) residue with queuine (Q) at position 34 (anticodon wobble position) in tRNAs with GU(N) anticodons (tRNA-Asp, -Asn, -His and -Tyr), resulting in the hypermodified nucleoside queuosine (7-(((4,5-cis-dihydroxy-2-cyclopenten-1-yl)amino)methyl)-7-deazaguanosine) (PubMed:11255023, PubMed:20354154, PubMed:34009357, PubMed:34241577). Catalysis occurs through a double-displacement mechanism. The nucleophile active site attacks the C1' of nucleotide 34 to detach the guanine base from the RNA, forming a covalent enzyme-RNA intermediate. The proton acceptor active site deprotonates the incoming queuine, allowing a nucleophilic attack on the C1' of the ribose to form the product (By similarity). Modification of cytoplasmic tRNAs with queuosine controls the elongation speed of cognate codons, thereby ensuring the correct folding of nascent proteins to maintain proteome integrity (PubMed:30093495)