Structural Studies of ABC Transporters and Oligosaccharyltransferase

Wednesday Afternoon Lecture Series Our understanding of the reaction mechanisms of membrane-embedded transport proteins or enzymes is insufficient. Dr. Kaspar Locher’s research group investigates two distinct types of membrane proteins, ATP-driven transporters and oligosaccaryltransferase (OST). In the past decade, his lab’s structural studies have defined the transmembrane folds of type 1 and type 2 ABC importers, ABC exporters, and of the catalytic subunit of OST. The first part of the lecture will focus on the mechanism of the bacterial ABC transporter BtuCD-F, which catalyzes vitamin B12 uptake into Gram-negative bacteria. The differences in mechanism to other ABC systems will be discussed, and an outlook on how structural biology might address unanswered mechanistic questions will be attempted. The second half of the lecture deals with OST catalyzing asparagine-linked (N-linked) protein glycosylation. This reaction is essential in eukaryotes and implicated in processes such as protein folding and quality control, organism development, or host-pathogen interactions. Some bacteria, including Campylobacter species, also catalyze N-linked glycosylation. Instead of a multimeric enzyme, they contain a single-subunit OST (PglB protein) that is homologous to the catalytically active subunit (STT3) of the eukaryotic system. The X-ray structure of the complete PglB protein from C. lari revealed the molecular basis of acceptor sequon recognition and provided insight into the r...
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