dol-P-Man:Man(7)GlcNAc(2)-PP-Dol alpha-1,6-mannosyltransferase activity / Biosynthesis of the N-glycan precursor (dolichol lipid-linked oligosaccharide, LLO) and transfer to a nascent protein / alpha-1,6-mannosyltransferase activity / dolichol-linked oligosaccharide biosynthetic process / protein N-linked glycosylation / 転移酵素; グリコシル基を移すもの; 六炭糖残基を移すもの / endoplasmic reticulum membrane 類似検索 - 分子機能
GPI mannosyltransferase / Alg9-like mannosyltransferase family 類似検索 - ドメイン・相同性
ジャーナル: Nat Chem Biol / 年: 2026 タイトル: Structures of ALG3/9/12 reveal the assembly logic of the N-glycan oligomannose core. 著者: J Andrew N Alexander / Shu-Yu Chen / Somnath Mukherjee / Mario de Capitani / Rossitza N Irobalieva / Lorenzo Rossi / Parth Agrawal / Julia Kowal / Matheus A Meirelles / Markus Aebi / Jean- ...著者: J Andrew N Alexander / Shu-Yu Chen / Somnath Mukherjee / Mario de Capitani / Rossitza N Irobalieva / Lorenzo Rossi / Parth Agrawal / Julia Kowal / Matheus A Meirelles / Markus Aebi / Jean-Louis Reymond / Anthony A Kossiakoff / Sereina Riniker / Kaspar P Locher / 要旨: Asparagine-linked glycans are essential for the maturation and function of most eukaryotic secretory proteins. The biosynthesis and transfer of dolichylpyrophosphate-anchored GlcNAcManGlc glycan is a ...Asparagine-linked glycans are essential for the maturation and function of most eukaryotic secretory proteins. The biosynthesis and transfer of dolichylpyrophosphate-anchored GlcNAcManGlc glycan is a highly conserved process occurring in the endoplasmic reticulum (ER) membrane and involving over a dozen membrane proteins whose dysfunction is linked to congenital disorders of glycosylation (CDGs). Three membrane-integral mannosyltransferases, ALG3, ALG9 and ALG12, mediate four consecutive mannosylation reactions that convert GlcNAcMan to GlcNAcMan. Here, using chemoenzymatically synthesized lipid-linked glycan donor and acceptor analogs, we recapitulated this biosynthetic pathway in vitro. High-resolution cryo-electron microscopy structures of pseudo-Michaelis complexes of each step revealed how the branched glycan is accurately synthesized and unwanted side products are averted. Molecular dynamics simulations and mutagenesis studies uncovered a subtle but precise mechanism selecting the dolichylphosphomannose donor substrate over dolichylphosphoglucose, which is also present in the ER membrane. Our results also provide mechanistic explanations for enzyme dysfunction in CDGs and offer opportunities for N-glycan engineering.