BIOSYNTHESIS OF THE CAPSULAR MATERIAL OF MYXOCOCCUS XANTHUS

Abstract

Purified capsular material of Myxococcus xanthus has previously been shown to be composed mainly of N-acetylgalactosamine, glucose and glycine. Investigations carried out during the last two years have demonstrated that UDP Gal NAc and UDP Glc are the major precursors. Biosynthesis of capsule was studied by measuring the incorporation of 140 _upp Gal NAc, 344-UDP Glc and Su-glycine into TCA insoluable material. All three compounds were incorporated more rapidly than into crude extracts prepared from 2 hr glycerol induced myxospores that in similar extracts prepared from vegetative cells. Preliminary studies indicated that incorporation of UDP Gal NAc was stimulated by UDP Glc and to a lesser degree by glycine and ATP. Similarly, incorporation of UDP Glc was stimulated by UDP Gal NAc, glycine and ATP. Both of the transferase activities were found exclusively in the 30,000 x g pellet, which were used for further studies. The glycine incorporating activity remained in the supernatant. Both transferase activities were linear with time for 1 hr and with protein concentration between 0.1 - 1.0 mg/ml. The incorporation of UDP Glc and UDP Gal NAc were absolutely dependent upon divalent cations and were inhibited 40 % by 100 pg/ml Bacitracin. In the absence of ATP, the incorporation of UDP Glc was stimulated by UDP Gal NAc, but UDP Gal NAc incorporation was not stimulated by various concentrations of UDP Gic. In both cases, the label was incorporated into the 30,000 x g pellet, from which it could be recovered as radioactive glucose and galactosamine following acid hydrolysis and paper chromatography.