Structural Bases for the Regulation of CO Binding in the Archaeal Protoglobin from Methanosarcina acetivorans.

PLoS ONE. 2015;10(6):e0125959 DOI 10.1371/journal.pone.0125959

 

Journal Homepage

Journal Title: PLoS ONE

ISSN: 1932-6203 (Online)

Publisher: Public Library of Science (PLoS)

LCC Subject Category: Medicine | Science

Country of publisher: United States

Language of fulltext: English

Full-text formats available: PDF, HTML, XML

 

AUTHORS


Lesley Tilleman

Stefania Abbruzzetti

Chiara Ciaccio

Giampiero De Sanctis

Marco Nardini

Alessandra Pesce

Filip Desmet

Luc Moens

Sabine Van Doorslaer

Stefano Bruno

Martino Bolognesi

Paolo Ascenzi

Massimo Coletta

Cristiano Viappiani

Sylvia Dewilde

EDITORIAL INFORMATION

Peer review

Editorial Board

Instructions for authors

Time From Submission to Publication: 24 weeks

 

Abstract | Full Text

Studies of CO ligand binding revealed that two protein states with different ligand affinities exist in the protoglobin from Methanosarcina acetivorans (in MaPgb*, residue Cys(E20)101 was mutated to Ser). The switch between the two states occurs upon the ligation of MaPgb*. In this work, site-directed mutagenesis was used to explore the role of selected amino acids in ligand sensing and stabilization and in affecting the equilibrium between the "more reactive" and "less reactive" conformational states of MaPgb*. A combination of experimental data obtained from electronic and resonance Raman absorption spectra, CO ligand-binding kinetics, and X-ray crystallography was employed. Three amino acids were assigned a critical role: Trp(60)B9, Tyr(61)B10, and Phe(93)E11. Trp(60)B9 and Tyr(61)B10 are involved in ligand stabilization in the distal heme pocket; the strength of their interaction was reflected by the spectra of the CO-ligated MaPgb* and by the CO dissociation rate constants. In contrast, Phe(93)E11 is a key player in sensing the heme-bound ligand and promotes the rotation of the Trp(60)B9 side chain, thus favoring ligand stabilization. Although the structural bases of the fast CO binding rate constant of MaPgb* are still unclear, Trp(60)B9, Tyr(61)B10, and Phe(93)E11 play a role in regulating heme/ligand affinity.