Structural basis of protein O‑mannosylation

 Protein glycosylation is an abundant and diverse post-translational modification, in which specific amino acids are covalently linked to carbohydrates. Three different types of protein glycosylation are initiated in the endoplasmic reticulum (ER), with the asparagine-linked glycosylation (N-glycosylation) and the protein O-mannosylation being the most prominent ones. Protein O-mannosylation is preserved across all kingdoms of life and essential in fungi and animals. Consequently, defects within the mannosylation machinery interfere with cell wall integrity and ER homeostasis in yeast, and often cause growth defects, embryonic lethality or severe congenital disorders of glycosylation (CDG). In eukaryotes, N-glycosylation is tightly linked to the import of membrane and secretory proteins into the ER predominantly via the SEC translocon or the tetrameric Sec63 complex. Interestingly, in yeast protein O-mannosylation can also occur adjacent to the SEC translocon, however, the exact mechanism of this interaction and its interplay with N-glycosylation need yet to be defined. One aim of this project is therefore to dissect the molecular mechanism of O-mannosylation and its link to protein translocation in yeast as a model system. We use a multi-disciplinary approach to gain insights into the structure and function of PMTs and POMTs, and their interaction with protein substrates. Another aim concerns asparagine-linked glycosylation (ALG) proteins as they perform the first steps in the synthesis pathway of the crucial lipid-linked oligosaccharide required for N-glycosylation of proteins.

Team

Irmgard Sinning (PI) has earned her PhD in Munich and is interested in molecular mechanisms of key cellular processes at the atomic level.

Karine Lapouge has earned her PhD in Orsay (France) and is an expert in biochemical and genetic studies in yeast and supports the project in all aspects dealing with the analysis of protein mechanisms.

Sofia Mortensen is a protein biochemist/structural biologist and earned her PhD at Aarhus (Denmark).

Silke Adrian is providing technical support for the project.

For more information on the Sinning lab visit her website.

COLLABORATIONS

We are collaborating with P2 Brügger on lipid binding and MS, P06 Schwalbe and P08 Strahl for NMR and functional analysis, P05 Ruppert on MS and XL-MS analysis, and P09 Thiel on in vivo and functional analysis of ALGs.