ANALYSIS OF THE PHA GRANULE-ASSOCIATED PROTEINS GA20 AND GA11 IN METHYLOBACTERIUM-EXTORQUENS AND METHYLOBACTERIUM-RHODESIANUM

Electrophoretic analysis of the proteins bound to poly(3-hydroxybutyri c acid), PHB-, granules in Methylobacterium extorquens, M. rhodesianum as well as the PHB-leaky mutants Mu 1 and Mu 11, which were isolated from the latter, resulted in two dominant low-molecular weight protein s, which were referred to as GA11 and GA20. After purification of thes e proteins antibodies against the GA11 and GA20 protein of M. extorque ns were obtained. Both proteins bound to the surface of PHB granules a s revealed by immunoelectron microscopy of whole cells of M. extorquen s and M. rhodesianum . With cells of the PHB-leaky mutants Mu 1 and Mu 11 no specific labeling was observed. The N-terminal amino acid seque nces of the GA11 and the GA20 protein were determined. We found signif icant homologies between the sequences of the investigated strains. Th e use of oligonucleotide probes based on the N-terminal sequences of t he GA20 protein from M. rhodesianum to identify the corresponding stru ctural genes in various genomic libraries failed.