Desulfovibrio vulgarisCbiKPcobaltochelatase: evolution of a haem binding protein orchestrated by the incorporation of two histidine residues

Lobo, Susana A.L. and Videira, Marco A.M. and Pacheco, Isabel and Wass, Mark N. and Warren, Martin J. and Teixeira, Miguel and Matias, Pedro M. and Romão, Célia V. and Saraiva, Lígia M. (2016) Desulfovibrio vulgarisCbiKPcobaltochelatase: evolution of a haem binding protein orchestrated by the incorporation of two histidine residues. Environmental Microbiology, 19 (1). pp. 106-118. ISSN 1462-2912. (In press) (doi:https://doi.org/10.1111/1462-2920.13479) (Access to this publication is currently restricted. You may be able to access a copy if URLs are provided)

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Abstract

The sulfate-reducing bacteria of the Desulfovibrio genus make three distinct modified tetrapyrroles, haem, sirohaem and adenosylcobamide, where sirohydrochlorin acts as the last common biosynthetic intermediate along the branched tetrapyrrole pathway. Intriguingly, D. vulgaris encodes two sirohydrochlorin chelatases, CbiKP and CbiKC, that insert cobalt/iron into the tetrapyrrole macrocycle but are thought to be distinctly located in the periplasm and cytoplasm respectively. Fusing GFP onto the C-terminus of CbiKP confirmed that the protein is transported to the periplasm. The structure-function relationship of CbiKP was studied by constructing eleven site-directed mutants and determining their chelatase activities, oligomeric status and haem binding abilities. Residues His154 and His216 were identified as essential for metal-chelation of sirohydrochlorin. The tetrameric form of the protein is stabilized by Arg54 and Glu76, which form hydrogen bonds between two subunits. His96 is responsible for the binding of two haem groups within the main central cavity of the tetramer. Unexpectedly, CbiKP is shown to bind two additional haem groups through interaction with His103. Thus, although still retaining cobaltochelatase activity, the presence of His96 and His103 in CbiKP, which are absent from all other known bacterial cobaltochelatases, has evolved CbiKP a new function as a haem binding protein permitting it to act as a potential haem chaperone or transporter.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Sciences > School of Biosciences
Depositing User: Sue Davies
Date Deposited: 10 Nov 2016 13:56 UTC
Last Modified: 09 Mar 2017 11:45 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/58529 (The current URI for this page, for reference purposes)
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