Frontiers in Chemical Biology (May 2024)
Effect of pH on the thermostability and redox properties of cytochrome c552 from Wolinella succinogenes
Abstract
Cytochrome c552 from Wolinella succinogenes is one of the few examples of a low reduction potential class I c-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 c-type cytochrome. The visible spectra obtained at different pH values reveal the presence of a protonable group with a pKa of 7.3, which also influences the reduction potential of this small cytochrome c552 (Em0’ of 97 ± 5 mV, pH 7.0) and can be either an H2O/OH− group distantly coordinating the heme iron, or one of the propionate groups. The thermostability of cytochrome c552 was studied by circular dichroism and differential scanning calorimetry, indicating a highly stable protein at pH 5–7 (90°C to 77°C).
Keywords
