Crystal structure of CobK reveals strand-swapping between Rossmann-fold domains and molecular basis of the reduced precorrin product trap

Gu, Shuang, Sushko, Oleksandr, Deery, Evelyne, Warren, Martin J. ORCID: https://orcid.org/0000-0002-6028-6456 and Pickersgill, Richard W. (2015) Crystal structure of CobK reveals strand-swapping between Rossmann-fold domains and molecular basis of the reduced precorrin product trap. Scientific Reports, 5. ISSN 2045-2322

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Abstract

CobK catalyzes the essential reduction of the precorrin ring in the cobalamin biosynthetic pathway. The crystal structure of CobK reveals that the enzyme, despite not having the signature sequence, comprises two Rossmann fold domains which bind coenzyme and substrate respectively. The two parallel β-sheets have swapped their last β-strands giving a novel sheet topology which is an interesting variation on the Rossmann-fold. The trapped ternary complex with coenzyme and product reveals five conserved basic residues that bind the carboxylates of the tetrapyrrole tightly anchoring the product. A loop, disordered in both the apoenzyme and holoenzyme structures, closes around the product further tightening binding. The structure is consistent with a mechanism involving protonation of C18 and pro-R hydride transfer from NADPH to C19 of precorrin-6A and reveals the interactions responsible for the specificity of CobK. The almost complete burial of the reduced precorrin product suggests a remarkable form of metabolite channeling where the next enzyme in the biosynthetic pathway triggers product release.

Item Type: Article
Uncontrolled Keywords: general ,/dk/atira/pure/subjectarea/asjc/1000
Faculty \ School: Faculty of Science
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Depositing User: LivePure Connector
Date Deposited: 20 Sep 2022 14:31
Last Modified: 27 Sep 2022 08:36
URI: https://ueaeprints.uea.ac.uk/id/eprint/88490
DOI: 10.1038/srep16943

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