AUTHOR=Mordido Vitor H. , Carepo Marta S. P. , Cordas Cristina M. , Paul Navendu , Simon Jörg , Moura Isabel , Pauleta Sofia R. 

TITLE=Effect of pH on the thermostability and redox properties of cytochrome c552 from Wolinella succinogenes

JOURNAL=Frontiers in Chemical Biology

VOLUME=3

YEAR=2024

URL=https://www.frontiersin.org/journals/chemical-biology/articles/10.3389/fchbi.2024.1398105

DOI=10.3389/fchbi.2024.1398105

ISSN=2813-530X

ABSTRACT=<p>Cytochrome <italic>c</italic><sub>552</sub> from <italic>Wolinella succinogenes</italic> is one of the few examples of a low reduction potential class I <italic>c</italic>-type cytochrome with a mixture of high/low spin state populations observed in its visible spectrum. Analysis of its structural model suggests that the heme is Met/His coordinated and highly solvent-exposed. This supports the hypothesis that it is the solvent accessibility of the propionate groups that controls the reduction potential of this small <italic>c</italic>-type cytochrome. The visible spectra obtained at different pH values reveal the presence of a protonable group with a p<italic>K</italic><sub>a</sub> of 7.3, which also influences the reduction potential of this small cytochrome <italic>c</italic><sub>552</sub> (E<sub>m</sub><sup>0’</sup> of 97 ± 5 mV, pH 7.0) and can be either an H<sub>2</sub>O/OH<sup>−</sup> group distantly coordinating the heme iron, or one of the propionate groups. The thermostability of cytochrome <italic>c</italic><sub>552</sub> was studied by circular dichroism and differential scanning calorimetry, indicating a highly stable protein at pH 5–7 (90°C to 77°C).</p>