ISOLATION AND IDENTIFICATION OF GRANULE-ASSOCIATED PROTEINS RELEVANT FOR POLY(3-HYDROXYALKANOIC ACID) BIOSYNTHESIS IN CHROMATIUM-VINOSUM D

Poly(3-hydroxybutyric acid) granules, which harbored only four major granule-associated proteins as revealed by SDS polyacrylamide gel electrophoresis, were isolated from crude cellular extracts of Chromatium vinosum D by centrifugation in a linear sucrose gradient. N-Terminal amino acid sequence determination identified two proteins of M(r) 41 000 and M(r) 40 000 as the phaE(Cv) and phaC(Cv) translational products, respectively, of C. vinosum D. In a previous study it was shown that both proteins are required for the expression of poly(3-hydroxyalkanoic acid) synthase activity. The N-terminus of the third protein (M(r) 17000) exhibited no homology to other proteins. Lysozyme, which was added during purification of the granules, exhibited a strong affinity to PHB granules and was identified as the fourth protein enriched with the granules.