Studies on algal cytochromes II. Some physical and chemical properties of further purified Petalonia cytochrome c-553.

Abstract

A cytochrome c-553 was isolated from a brown alga, Petalonia fascia, and its physical and chemical properties were investigated. At liquid nitrogen temperature, the α-, β- and γ-band of this cytochrome shifted 1-2 nm to the shorter wavelength in comparison with those at room temperature. The α-band split into two peaks, 551.5 (major band) and 546.5 nm (minor band), at the low temperature. The cytochrome in high concentration showed a shoulder at 695 nm in its oxidized state, suggesting a methionine residue to be the sixth ligand of heme iron. The molecular weight was estimated to be about 10,000 containing one mole of heme c based on analyses of gel filtration, sodium dodecyl sulfate acrylamide gel electrophoresis, amino acid composition and iron content. The isoelectric points of the ferro- and ferricytochromes were estimated to be at pH 4.1 and 4.3, respectively, by the isoelectric focusing method. The amino acid composition of this cytochrome was Lys6, Arg1, Asp15, Thr5, Ser6, Glu11, Pro2, Gly7, Ala7, Cys2, Val6, Met3, Ile6, Leu3, Tyr1, Phe3, Trp1, with a total of 86 residues. The amino- and carboxylterminal sequences and four chymotryptic peptide sequences were compared with those of other cytochromes c to show that these cytochromes were homologous to one another.