9.B.142.5.6 The structure of the yeast O-mannosyltransferase Pmt1-Pmt2 complex has been determined at 3.2 Å resolution (Bai et al. 2019). In eukaryotes, a nascent peptide entering the endoplasmic reticulum (ER) is scanned by two Sec61 translocon-associated large membrane machines for protein N-glycosylation and protein O-mannosylation, respectively. The structures of both the eight-protein oligosaccharyltransferase complex and the mannosyltransferases of the PMT family have been determined. They function in ER protein homeostasis. Cryo-EM structures of the Saccharomyces cerevisiae Pmt1-Pmt2 complex bound to a donor and an acceptor peptide shows that each subunit contains 11 TMSs and a lumenal beta-trefoil fold termed the MIR domain. The structures reveal the substrate recognition site and confirms an inverting mannosyl-transferring reaction mechanism. The transmembrane domains of Pmt1 and Pmt2 share a structural fold with the catalytic subunits of oligosaccharyltransferases, confirming an evolutionary relationship between protein O-mannosylation and protein N-glycosylation (Bai et al. 2019).
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Accession Number: | P33775 |
Protein Name: | Dolichyl-phosphate-mannose--protein mannosyltransferase 1 |
Length: | 817 |
Molecular Weight: | 92675.00 |
Species: | Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast) [559292] |
Number of TMSs: | 9 |
Location1 / Topology2 / Orientation3: |
Endoplasmic reticulum membrane1 / Multi-pass membrane protein2 |
Substrate |
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1: MSEEKTYKRV EQDDPVPELD IKQGPVRPFI VTDPSAELAS LRTMVTLKEK LLVACLAVFT
61: AVIRLHGLAW PDSVVFDEVH FGGFASQYIR GTYFMDVHPP LAKMLYAGVA SLGGFQGDFD
121: FENIGDSFPS TTPYVLMRFF SASLGALTVI LMYMTLRYSG VRMWVALMSA ICFAVENSYV
181: TISRYILLDA PLMFFIAAAV YSFKKYEMYP ANSLNAYKSL LATGIALGMA SSSKWVGLFT
241: VTWVGLLCIW RLWFMIGDLT KSSKSIFKVA FAKLAFLLGV PFALYLVFFY IHFQSLTLDG
301: DGASFFSPEF RSTLKNNKIP QNVVADVGIG SIISLRHLST MGGYLHSHSH NYPAGSEQQQ
361: STLYPHMDAN NDWLLELYNA PGESLTTFQN LTDGTKVRLF HTVTRCRLHS HDHKPPVSES
421: SDWQKEVSCY GYSGFDGDAN DDWVVEIDKK NSAPGVAQER VIALDTKFRL RHAMTGCYLF
481: SHEVKLPAWG FEQQEVTCAS SGRHDLTLWY VENNSNPLLP EDTKRISYKP ASFISKFIES
541: HKKMWHINKN LVEPHVYESQ PTSWPFLLRG ISYWGENNRN VYLLGNAIVW WAVTAFIGIF
601: GLIVITELFS WQLGKPILKD SKVVNFHVQV IHYLLGFAVH YAPSFLMQRQ MFLHHYLPAY
661: YFGILALGHA LDIIVSYVFR SKRQMGYAVV ITFLAASVYF FKSFSPIIYG TPWTQELCQK
721: SQWLSGWDYN CNTYFSSLEE YKNQTLTKRE SQPAATSTVE EITIEGDGPS YEDLMNEDGK
781: KIFKDTEGNE LDPEVVKKML EEEGANILKV EKRAVLE