Structure of bacterial oligosaccharyltransferase PglB bound to a reactive LLO and an inhibitory peptide

Napiórkowska, Maja; Boilevin, Jérémy; Darbre, Tamis; Reymond, Jean-Louis; Locher, Kaspar P. (2018). Structure of bacterial oligosaccharyltransferase PglB bound to a reactive LLO and an inhibitory peptide. Scientific Reports, 8(1) Nature Publishing Group 10.1038/s41598-018-34534-0

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Oligosaccharyltransferase (OST) is a key enzyme of the N-glycosylation pathway, where it catalyzes the transfer of a glycan from a lipid-linked oligosaccharide (LLO) to an acceptor asparagine within the conserved sequon N-X-T/S. A previous structure of a ternary complex of bacterial single subunit OST, PglB, bound to a non-hydrolyzable LLO analog and a wild type acceptor peptide showed how both substrates bind and how an external loop (EL5) of the enzyme provided specific substrate-binding contacts. However, there was a relatively large separation of the substrates at the active site. Here we present the X-ray structure of PglB bound to a reactive LLO analog and an inhibitory peptide, revealing previously unobserved interactions in the active site. We found that the atoms forming the N-glycosidic bond (C-1 of the GlcNAc moiety of LLO and the –NH2 group of the peptide) are closer than in the previous structure, suggesting that we have captured a conformation closer to the transition state of the reaction. We find that the distance between the divalent metal ion and the glycosidic oxygen of LLO is now 4 Å, suggesting that the metal stabilizes the leaving group of the nucleophilic substitution reaction. Further, the carboxylate group of a conserved aspartate of PglB mediates an interaction network between the reducing-end sugar of the LLO, the asparagine side chain of the acceptor peptide, and a bound divalent metal ion. The interactions identified in this novel state are likely to be relevant in the catalytic mechanisms of all OSTs.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Boilevin, Jérémy Mathias; Darbre, Tamis and Reymond, Jean-Louis

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

2045-2322

Publisher:

Nature Publishing Group

Language:

English

Submitter:

Sandra Tanja Zbinden Di Biase

Date Deposited:

19 Dec 2018 14:19

Last Modified:

23 Dec 2018 02:33

Publisher DOI:

10.1038/s41598-018-34534-0

BORIS DOI:

10.7892/boris.122707

URI:

https://boris.unibe.ch/id/eprint/122707

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