Abstact

An interplay between the structural and physicochemical properties of the monoheme cytochromes of type c has been extensively studied. However new proteins belonging to this diverse family continue to reveal some novel and unique features. Here, we present the 1.15 Å structure of the low-potential cytochrome c546/556 from the bacterium Thioalkalivibrio paradoxus ARh1, which exhibits the prominent splitting of the Q bands in UV-visible spectra even at room temperature. The data obtained suggest that two conformations of the propionate 7 of the heme are responsible for the splitting of the Q bands. We propose that the degree of the splitting of the Q bands is correlated with the conformational lability of the heme propionates.