The cytochrome c(3) superfamily includes Desulfovibrio polyheme cytoch
romes c. We report the characteristic thermal stability parameters of
the Desalfovibrio desulfuricans Norway (D.d.N.) cytochromes c(3) (M(r)
13,000 and M(r) 26,000) and the Desulfovibrio vulgaris Hildenborough
(D.v.H.) cytochrome c(3) (M(r) 13,000) and high molecular mass cytochr
ome c (Hmc), as obtained with the help of electronic spectroscopy, vol
tammetric techniques and differential scanning calorimetry. The polyhe
me cytochromes are denatured over a wide range of temperatures: the D.
v.H. cytochrome c(3) is highly thermostable (T-d = 121 degrees C) cont
rary to the D.d.N. protein (T-d = 73 degrees C), The thermostability o
f the polyheme cytochromes is redox state dependent. The results are d
iscussed in the light of the structural and functional relationships w
ithin the cytochrome c(3) superfamily.