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Evolution in a family of chelatases facilitated by the introduction of active site asymmetry and protein oligomerization

DOI: 10.1073/pnas.1014298108 DOI Help
PMID: 21173279 PMID Help

Authors: Celia V. Romao (Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa) , Dimitrios Ladakis (University of Kent) , Susana A. L. Lobo (Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa) , Maria A. Carrondo (Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa) , Amanda A. Brindley (University of Kent) , Evelyne Deery (University of Kent) , Pedro M. Matias (Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa) , Richard W. Pickersgill (Queen Mary University of London) , Ligia M. Saraiva (Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa) , Mark Warren (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 108 (1) , PAGES 97 - 102

State: Published (Approved)
Published: January 2011
Diamond Proposal Number(s): 7197

Abstract: The class II chelatases associated with heme, siroheme, and cobalamin biosynthesis are structurally related enzymes that insert a specific metal ion (Fe2+ or Co2+) into the center of a modified tetrapyrrole (protoporphyrin or sirohydrochlorin). The structures of two related class II enzymes, CbiXS from Archaeoglobus fulgidus and CbiK from Salmonella enterica, that are responsible for the insertion of cobalt along the cobalamin biosynthesis pathway are presented in complex with their metallated product. A further structure of a CbiK from Desulfovibrio vulgaris Hildenborough reveals how cobalt is bound at the active site. The crystal structures show that the binding of sirohydrochlorin is distinctly different to porphyrin binding in the protoporphyrin ferrochelatases and provide a molecular overview of the mechanism of chelation. The structures also give insights into the evolution of chelatase form and function. Finally, the structure of a periplasmic form of Desulfovibrio vulgaris Hildenborough CbiK reveals a novel tetrameric arrangement of its subunits that are stabilized by the presence of a heme b cofactor. Whereas retaining colbaltochelatase activity, this protein has acquired a central cavity with the potential to chaperone or transport metals across the periplasmic space, thereby evolving a new use for an ancient protein subunit.

Journal Keywords: Catalytic; Cobalt; Crystallization; Desulfovibrio; Evolution; Molecular; Ferrochelatase; Models; Molecular; Multigene; Porphyrins; Salmonella; Uroporphyrins; Vitamin B 12

Subject Areas: Biology and Bio-materials


Instruments: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I04-Macromolecular Crystallography , I24-Microfocus Macromolecular Crystallography

Other Facilities: ESRF