Abstract: The N-terminal amino acid sequence of the polyhydroxyalkanoic acid (PHA) granule-associated M.sub.r 15,500 protein of Rhodococcus ruber, which is referred to as the GA14-protein, was analysed. The sequence revealed that the corresponding structural gene is represented by the open reading frame 3 encoding a protein with a calculated M.sub.r 14,175 which was recently localized downstream of the PHA synthase gene (Pieper, U., and A. Steinbuchel, 1992. FEMS Microbiol. Lett. 96: 73-80). A recombinant strain of Escherichia coli XL1-Blue carrying the hybrid plasmid (pSKXA10*) with ORF3 overexpressed the GA14-protein. The GA14-protein was subsequently purified in a three-step procedure including chromatography on DEAE-Sephacel, Phenyl-Sepharose CL-4B and Superose 12. Determination of the molecular weight by gel filtration as well as electron microscopic studies make a tetrameric structure of the recombinant, native GA14-protein most likely.