Alanine to serine substitutions drive thermal adaptation in a psychrophilic diatom cytochrome c.

In this study, we investigate the thermodynamic mechanisms by which electron transfer proteins adapt to environmental temperature by directly comparing the redox properties and folding stability of a psychrophilic cytochrome c and a mesophilic homolog. Our model system consists of two cytochrome c proteins from diatoms: one adapted specifically to polar environments, the other adapted generally to surface ocean environments. Direct electrochemistry shows that the midpoint potential for the mesophilic homolog is slightly higher at all temperatures measured.