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ID 48209
file
creator
Adams, Hannah R.
Krewson, Callie
Vardanega, Jenny E.
Moreno, Tadeo
Chicano
Svistunenko, Dimitri
Paps, Jordi
Andrew, Colin R.
Hough, Michael A.
abstract
Nature is adept at utilising highly similar protein folds to carry out very different functions, yet the mechanisms by which this functional divergence occurs remain poorly characterised. In certain methanotrophic bacteria, two homologous pentacoordinate c-type heme proteins have been identified: a cytochrome P460 (cyt P460) and a cytochrome c0-b (cyt cp-b). Cytochromes P460 are able to convert hydroxylamine to nitrous oxide (N2O), a potent greenhouse gas. This reactivity is similar to that of hydroxylamine oxidoreductase (HAO), which is a key enzyme in nitrifying and methanotrophic bacteria. Cyt P460 and HAO both have unusual protein-heme cross-links, formed by a Tyr residue in HAO and a Lys in cyt P460. In contrast, cyts cp-b (the only known cytochromes c0 with a b-sheet fold) lack this crosslink and appears to be optimized for binding non-polar molecules (including NO and CO) without enzymatic conversion. Our bioinformatics analysis supports the proposal that cyt cp-b may have evolved from cyt P460 via a gene duplication event. Using high-resolution X-ray crystallography, UV-visible absorption, electron paramagnetic resonance (EPR) and resonance Raman spectroscopy, we have characterized the overall protein folding and active site structures of cyt cp-b and cyt P460 from the obligate methanotroph, Methylococcus capsulatus (Bath). These proteins display a similar b-sheet protein fold, together with a pattern of changes to the heme pocket regions and localised tertiary structure that have converted a hydroxylamine oxidizing enzyme into a gas-binding protein. Structural comparisons provide insights relevant to enzyme redesign for synthetic enzymology and engineering of gas sensor proteins. We also show the widespread occurrence of cyts cp-b and characterise their phylogeny.
description
CRA acknowledges funding from the National Science Foundation (grant MCB 1411963). TMC was supported by Leverhulme Trust award RPG-2014-355 to MAH.
journal title
Chemical Science
volume
Volume 10
issue
Issue 10
start page
3031
end page
3041
date of issued
2019-01-21
publisher
Royal Society of Chemistry
issn
2041-6520
2041-6539
publisher doi
language
eng
nii type
Journal Article
HU type
Journal Articles
DCMI type
text
format
application/pdf
text version
publisher
rights
© The Royal Society of Chemistry 2019
This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
relation
Electronic supplementary information (ESI) available. See DOI: 10.1039/c8sc05210g
relation url
department
Graduate School of Biosphere Science



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