Methionine synthase reductase (MSR) (EC 1.16.1.8) (Aquacobalamin reductase) (AqCbl reductase)
1_MRRFL 6_ LLYAT 11_ QQGQA 16_ KAIAE 21_ EICEQ 26_ AVVHG 31_ FSADL 36_ HCISE 41_ SDKYD 46_ LKTET 51_ APLVV 56_ VVSTT 61_ GTGDP 66_ PDTAR 71_ KFVKE 76_ IQNQT 81_ LPVDF 86_ FAHLR 91_ YGLLG 96_ LGDSE 101_ YTYFC 106_ NGGKI 111_ IDKRL 116_ QELGA 121_ RHFYD 126_ TGHAD 131_ DCVGL 136_ ELVVE 141_ PWIAG 146_ LWPAL 151_ RKHFR 156_ SSRGQ 161_ EEISG 166_ ALPVA 171_ SPASS 176_ RTDLV 181_ KSELL 186_ HIESQ 191_ VELLR 196_ FDDSG 201_ RKDSE 206_ VLKQN 211_ AVNSN 216_ QSNVV 221_ IEDFE 226_ SSLTR 231_ SVPPL 236_ SQASL 241_ NIPGL 246_ PPEYL 251_ QVHLQ 256_ ESLGQ 261_ EESQV 266_ SVTSA 271_ DPVFQ 276_ VPISK 281_ AVQLT 286_ TNDAI 291_ KTTLL 296_ VELDI 301_ SNTDF 306_ SYQPG 311_ DAFSV 316_ ICPNS 321_ DSEVQ 326_ SLLQR 331_ LQLED 336_ KREHC 341_ VLLKI 346_ KADTK 351_ KKGAT 356_ LPQHI 361_ PAGCS 366_ LQFIF 371_ TWCLE 376_ IRAIP 381_ KKAFL 386_ RALVD 391_ YTSDS 396_ AEKRR 401_ LQELC 406_ SKQGA 411_ ADYSR 416_ FVRDA 421_ CACLL 426_ DLLLA 431_ FPSCQ 436_ PPLSL 441_ LLEHL 446_ PKLQP 451_ RPYSC 456_ ASSSL 461_ FHPGK 466_ LHFVF 471_ NIVEF 476_ LSTAT 481_ TEVLR 486_ KGVCT 491_ GWLAL 496_ LVASV 501_ LQPNI 506_ HASHE 511_ DSGKA 516_ LAPKI 521_ SISPR 526_ TTNSF 531_ HLPDD 536_ PSIPI 541_ IMVGP 546_ GTGIA 551_ PFIGF 556_ LQHRE 561_ KLQEQ 566_ HPDGN 571_ FGAMW 576_ LFFGC 581_ RHKDR 586_ DYLFR 591_ KELRH 596_ FLKHG 601_ ILTHL 606_ KVSFS 611_ RDAPV 616_ GEEEA 621_ PAKYV 626_ QDNIQ 631_ LHGQQ 636_ VARIL 641_ LQENG 646_ HIYVC 651_ GDAKN 656_ MAKDV 661_ HDALV 666_ QIISK 671_ EVGVE 676_ KLEAM 681_ KTLAT 686_ LKEEK 691_RYLQD
1: Key enzyme in methionine and folate homeostasis responsible for the reactivation of methionine synthase (MTR/MS) activity by catalyzing the reductive methylation of MTR-bound cob(II)alamin (PubMed:17892308). Cobalamin (vitamin B12) forms a complex with MTR to serve as an intermediary in methyl transfer reactions that cycles between MTR-bound methylcob(III)alamin and MTR bound-cob(I)alamin forms, and occasional oxidative escape of the cob(I)alamin intermediate during the catalytic cycle leads to the inactive cob(II)alamin species (Probable). The processing of cobalamin in the cytosol occurs in a multiprotein complex composed of at least MMACHC, MMADHC, MTRR and MTR which may contribute to shuttle safely and efficiently cobalamin towards MTR in order to produce methionine (PubMed:27771510). Also necessary for the utilization of methyl groups from the folate cycle, thereby affecting transgenerational epigenetic inheritance (By similarity). Also acts as a molecular chaperone for methionine synthase by stabilizing apoMTR and incorporating methylcob(III)alamin into apoMTR to form the holoenzyme (PubMed:16769880). Also serves as an aquacob(III)alamin reductase by reducing aquacob(III)alamin to cob(II)alamin; this reduction leads to stimulation of the conversion of apoMTR and aquacob(III)alamin to MTR holoenzyme (PubMed:16769880)