The Complete Amino Acid Sequence of Both Subunits of C-Phycocyanin from the CyanobacteriumMastigocladus laminosus

Abstract

The amino acid sequences of both subunits of the C-phycocyanin from the thermophilic cyanobacterium M. laminosus were determined. The .alpha.-chain consists of 162 amino acid residues and has a MW of 18,000, whereas the .beta.-chain consists of 172 residues and has a MW of 19,400. For the first 3/4 of their length the polypeptide chains are 31% homologous, whereas there is no significant homology in the final quarter up to the C-terminus. This could mean that the introduction of an additional chromophore binding site in the last quarter of the .beta.-chain during evolution was achieved via a large number of point mutations or by exchange of the whole C-terminal part in an ancestral gene.