ISOLATION AND PURIFICATION OF GRANULE-ASSOCIATED PROTEINS RELEVANT FOR POLY(3-HYDROXYBUTYRIC ACID) BIOSYNTHESIS FROM METHYLOTROPHIC BACTERIA RELYING ON THE SERINE PATHWAY

The poly(3-hydroxybutyric acid) (PHB) granules from eight methylotroph ic bacteria that use the serine pathway were isolated in a sucrose gra dient (1-2 M); these bacteria included members of the genus Methylobac terium, Mycoplana rubra, and PHB-leaky mutants of Methylobacterium rho desianum. As shown by sodium dodecyl sulfate - polyacrylamide gel elec trophoresis, the granules from all investigated methylotrophic strains revealed two major bands representing small proteins. An efficient pu rification procedure for these two low molecular weight proteins assoc iated with the PHB granules was developed by solubilization of the pro teins with Triton X-114 and affinity chromatography on Procion Blue-H- ERD.