3wai | pdb_00003wai
Crystal structure of the C-terminal globular domain of oligosaccharyltransferase (AfAglB-L, O29867_ARCFU) from Archaeoglobus fulgidus as a MBP fusion
Structural highlights
FunctionMALE_ECOLI Involved in the high-affinity maltose membrane transport system MalEFGK. Initial receptor for the active transport of and chemotaxis toward maltooligosaccharides.AGLB3_ARCFU Oligosaccharyl transferase (OST) that catalyzes the initial transfer of a defined glycan (a glucose-linked heptasaccharide composed of 3 Glc, 2 Man, 2 Gal and a sulfate for A.fulgidus AglB-L) from the lipid carrier dolichol-monophosphate to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains, the first step in protein N-glycosylation.[1] [2] [3] Publication Abstract from PubMedBACKGROUND: Protein N-glycosylation occurs in the three domains of life. Oligosaccharyltransferase (OST) transfers an oligosaccharide chain to the asparagine residue in the N-glycosylation sequons. The catalytic subunits of the OST enzyme are STT3 in eukaryotes, AglB in archaea and PglB in eubacteria. The genome of a hyperthermophilic archaeon, Archaeoglobus fulgidus, encodes three paralogous AglB proteins. We previously solved the crystal structures of the C-terminal globular domains of two paralogs, AglB-Short 1 and AglB-Short 2. RESULTS: We determined the crystal structure of the C-terminal globular domain of the third AglB paralog, AglB-Long, at 1.9 A resolutions. The crystallization of the fusion protein with maltose binding protein (MBP) afforded high quality protein crystals. Two MBP-AglB-L molecules formed a swapped dimer in the crystal. Since the fusion protein behaved as a monomer upon gel filtration, we reconstituted the monomer structure from the swapped dimer by exchanging the swapped segments. The C-terminal domain of A. fulgidus AglB-L includes a structural unit common to AglB-S1 and AglB-S2. This structural unit contains the evolutionally conserved WWDYG and DK motifs. The present structure revealed that A. fulgidus AglB-L contained a variant type of the DK motif with a short insertion, and confirmed that the second signature residue, Lys, of the DK motif participates in the formation of a pocket that binds to the serine and threonine residues at the +2 position of the N-glycosylation sequon. CONCLUSIONS: The structure of A. fulgidus AglB-L, together with the two previously solved structures of AglB-S1 and AglB-S2, provides a complete overview of the three AglB paralogs encoded in the A. fulgidus genome. All three AglBs contain a variant type of the DK motif. This finding supports a previously proposed rule: The STT3/AglB/PglB paralogs in one organism always contain the same type of Ser/Thr-binding pocket. The present structure will be useful as a search model for molecular replacement in the structural determination of the full-length A. fulgidus AglB-L. Crystal structure of the C-terminal globular domain of the third paralog of the Archaeoglobus fulgidus oligosaccharyltransferases.,Matsumoto S, Shimada A, Kohda D BMC Struct Biol. 2013 Jul 1;13(1):11. PMID:23815857[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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