The isolation of poly(3-hydroxybutyric acid) granules of Chromatium vinosum D was re-examined. Beside the PHA synthase and a 17 kDa protein, a 14 kDa protein was identified as predominant granule-associated protein. The M(r) as well as the N-terminal amino acid sequence exhibited identity to ORF5(Cv), which is located within the pha-locus of C. vinosum. In addition, sequence alignements revealed new information about ORF4(Cv), which is also located within the pha-locus, and about the 17 kDa protein, which exhibited homology to heat shock proteins recently detected in Escherichia coli.