Cyanophycin granule polypeptide in a facultatively heterotrophic cyanobacterium

Cyanophycin granule polypeptide (CGP) formation and degradation was studied in a facultatively heterotrophic, nitrogen-fixing cyanobacterium. CGP was synthesized primarily under photoautotrophic growth conditions in nitrogen-fixing cells. Addition of a utilizable carbon source stopped CGP synthesis, the content of which declined in cultures as the cells grew heterotrophically in light or dark. A high-performance liquid chromatographic method was developed to determine CGP in cyanobacterial extracts and permitted analyses of CGP and simultaneous examination of the protein profile of the cells. The data indicated that, once formed in the photoautotrophs, CGP was not degraded, even by cells in which extensive protein breakdown was occurring.