Biological Sciences Division
Published January 5, 2023 | Version v1
Journal article Open

Structure, sequon recognition and mechanism of tryptophan C-mannosyltransferase

Creators

  • 1. Howard Hughes Medical Institute
  • 2. Walter and Eliza Hall Institute of Medical Research
  • 3. University of Chicago
  • 4. University of Bern
  • 5. ETH Zürich
  • 6. University of Melbourne

Description

C-linked glycosylation is essential for the trafficking, folding and function of secretory and transmembrane proteins involved in cellular communication processes. The tryptophan C-mannosyltransferase (CMT) enzymes that install the modification attach a mannose to the first tryptophan of WxxW/C sequons in nascent polypeptide chains by an unknown mechanism. Here, we report cryogenic-electron microscopy structures of Caenorhabditis elegans CMT in four key states: apo, acceptor peptide-bound, donor-substrate analog-bound and as a trapped ternary complex with both peptide and a donor-substrate mimic bound. The structures indicate how the C-mannosylation sequon is recognized by this CMT and its paralogs, and how sequon binding triggers conformational activation of the donor substrate: a process relevant to all glycosyltransferase C superfamily enzymes. Our structural data further indicate that the CMTs adopt an unprecedented electrophilic aromatic substitution mechanism to enable the C-glycosylation of proteins. These results afford opportunities for understanding human disease and therapeutic targeting of specific CMT paralogs.

Data availability

Atomic coordinates of the CeDPY19 models have been deposited in RCSB Protein Data Bank under accession numbers 7ZLH (apo), 7ZLH (peptide-bound), 7ZLI (Dol25-P-Man-bound) and 7ZLJ (Dol25-P-C-Man- and peptide-bound). The three-dimensional cryo-EM maps were deposited in the Electron Microscopy Data Bank under accession numbers EMD-14780 (apo), EMD-14779 (peptide-bound), EMD-14781 (Dol25-P-Man-bound) and EMD-14782 (Dol25-P-C-Man- and peptide-bound). MS data to quantitate tryptophan C-mannosyaltion on RNAse2 has been deposited to the PRIDE proteomics repository under the accession number: PXD032391 using the username reviewer_pxd032391@ebi.ac.uk and password sItWEoNT. Source data are provided with this paper.

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Additional details

Identifiers

DOI
10.1038/s41589-022-01219-9
Other
oai:uchicago.tind.io:10272

Funding

Swiss National Science Foundation
CRSII5_173709
Swiss National Science Foundation
310030_196862
ETH
Research grant
National Institutes of Health
GM117372
NHMRC
GNT1139546
NHMRC
GNT2000517
Brian M. Davis Charitable Foundation
Fellowship
ARC
Future Fellowship
Discovery Project
DP210100362

UChicago Information

Division(s)
Biological Sciences Division
Department(s)
Biochemistry and Molecular Biology