The amino acid sequence of cytochrome f from the brown alga Alaria esculenta (L.) Grev

Cloning, expression and purification of cytochrome c(6) from the brown alga Hizikia fusiformis and complete X-ray diffraction analysis of the structure

The primary sequence of cytochrome c(6) from the brown alga Hizikia fusiformis has been determined by cDNA cloning and the crystal structure has been solved at 1.6 A resolution. The crystal belonged to the tetragonal space group P4(1)2(1)2, with unit-cell parameters a = b = 84.58, c = 232.91 A and six molecules per asymmetric unit. The genome code, amino-acid sequence and crystal structure of H. fusiformis cytochrome c(6) were most similar to those of red algal cytochrome c(6). These results support the hypothesis that brown algae acquired their chloroplasts via secondary endosymbiosis involving a red algal endosymbiont and a eukaryote host.

Purification and primary structure of cytochrome f from the cyanobacterium, Plectonema boryanum

The amino acid sequence of the soluble c-type cytochrome, cytochrome f, from the cyanobacterium Plectonema boryanum (also called Phormidium luridum or Schizothrix calcicola) has been determined. The proposed sequence consists of one polypeptide chain of 85 residues and has three Asn-Gly linkages. Partly due to the presence of these Asn-Gly bonds, which readily undergo rearrangement, proteolytic digestion on the small amount of protein available was unsatisfactory. The structure was determined partly by a combination of chemical cleavage and automatic sequencing techniques. A new technique for conserving material by cyanogen bromide cleavage of residual polypeptide after automatic degradation is described. The possible evolutionary significance of primary structure comparisons with other cytochromes f is discussed.