Structural characterization of the cyanophycin granule polypeptide of Anabaena cylindrica by circular dichroism and Raman spectroscopy.

The cyanophycin granule polypeptide, or multi-L-arginyl-poly(L-aspartic acid), from the filamentous cyanobacterium Anabaena cylindrica has been examined by circular dichroism and laser Raman spectroscopy. The polypeptide exhibits defined secondary structure in acidic solution, but not in alkaline medium. Raman spectra show the structure of the insoluble (storage?) form of the polypeptide is similar but not identical to that of the acid soluble form. Analysis of the CD spectra suggests that beta-sheets exist in the acid soluble form, and by inference, in the insoluble cellular material.