INTERFACIAL PROPERTIES OF THE POLYHEME CYTOCHROME C(3) SUPERFAMILY FROM DESULFOVIBRIO

In order to compare the interfacial behavior of the polyheme cytochrom es c which belong to the cytochrome c(3) superfamily, the monomolecula r film technique was used to determine whether and how these metallopr oteins interact with (phospho)lipids. Measurements of the variations o f surface pressure and surface potential versus time have shown differ ences in their penetration capacity into phosphatidylcholine, dicaprin , and phosphatidylglycerol films. The Desulfovibrio vulgaris Hildenbor ough cytochrome with 16 hemes (Hmc) and Desulfovibrio desulfuricans No rway tetra- and octaheme cytochromes c(3), which have been assumed to be soluble periplasmic molecules, may be considered as extrinsic membr ane proteins, unlike the D. vulgaris Hildenborough cytochrome c(3) (M( r) 13 000). The interfacial properties are discussed in terms of the a vailable three-dimensional structural data, the electrostatic potentia l calculation, and the results obtained by hydrophobic cluster analysi s of the cytochrome sequences. The very different behavior of the two cytochromes c(3) (M, 13 000) enlightens the role of a particular surfa ce loop in the interaction with a model membrane. A functional interpr etation is proposed assuming that the D. vulgaris Hildenborough Hmc an d both cytochromes c(3) (M(r) 13 000) and (M(r) 26 000) from the Norwa y strain might provide the link between periplasmic hydrogen oxidation and cytoplasmic sulfate reduction.