Studies on algal cytochromes II. Some physical and chemical properties of further purified Petalonia cytochrome c-553
1980
Sugimura, Yasutomo | Wada, Keishiro | Matsubara, Hiroshi
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 Lys ₆, Arg ₁, Asp ₁₅, Thr ₅, Ser ₆, Glu ₁₁, Pro ₂, Gly ₇, Ala ₇, Cys ₂, Val ₆, Met ₃, Ile ₆, Leu ₃, Tyr ₁, Phe ₃, Trp ₁, 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.
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