THERMAL-STABILITY OF THE POLYHEME CYTOCHROME C(3) SUPERFAMILY

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.