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A Membrane‐Bound Cytochrome c 3 : A Type II Cytochrome c 3 from Desulfovibrio vulgaris Hildenborough
Author(s) -
Valente Filipa M. A.,
Saraiva Lígia M.,
LeGall Jean,
Xavier António V.,
Teixeira Miguel,
Pereira Inês A. C.
Publication year - 2001
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/1439-7633(20011203)2:12<895::aid-cbic895>3.0.co;2-v
Subject(s) - desulfovibrio vulgaris , cytochrome , cytochrome c , biochemistry , heme , desulfovibrio , chemistry , hydrogenase , cytochrome c1 , coenzyme q – cytochrome c reductase , cytochrome b , cytochrome p450 reductase , biology , gene , bacteria , enzyme , genetics , mitochondrion , mitochondrial dna
A new tetraheme cytochrome c 3 was isolated from the membranes of Desulfovibrio vulgaris Hildenborough ( Dv H). This cytochrome has a molecular mass of 13.4 kDa and a pI of 5.5 and contains four heme c groups with apparent reduction potentials of −170 mV, −235 mV, −260 mV and −325 mV at pH 7.6. The complete sequence of the new cytochrome, retrieved from the preliminary data of the Dv H genome, shows that this cytochrome is homologous to the “acidic” cytochrome c 3 from Desulfovibrio africanus ( Da ). A model for the structure of the Dv H cytochrome was built based on the structure of the Da cytochrome. Both cytochromes share structural features that distinguish them from other cytochrome c 3 proteins, such as a solvent‐exposed heme 1 surrounded by an acidic surface area, and a heme 4 which lacks most of the surface lysine patch proposed to be the site of hydrogenase interaction in other cytochrome c 3 proteins. Furthermore, in contrast to previously discovered cytochrome c 3 proteins, the genes coding for these two cytochromes are adjacent to genes coding for two membrane‐associated FeS proteins, which indicates that they may be part of membrane‐bound oxidoreductase complexes. Altogether these observations suggest that the Dv H and Da cytochromes are a new type of cytochrome c 3 proteins (Type II: TpII‐ c 3 ) with different redox partners and physiological function than the other cytochrome c 3 proteins (Type I: TpI‐ c 3 ). The Dv H TpII‐ c 3 is reduced at considerable rates by the two membrane‐bound [NiFe] and [NiFeSe] hydrogenases, but catalytic amounts of TpI‐ c 3 increase these rates two‐ and fourfold, respectively. With the periplasmic [Fe] hydrogenase TpII‐ c 3 is reduced much slower than TpI‐ c 3 , and no catalytic effect of TpI‐ c 3 is observed.