Protein phosphorylation in Bacillus thuringiensis during growth and delta-endotoxin production

At least 14 phosphopolypeptides in which the phosphate groups were present as mono-esters were detected by pulse labelling of Bacillus thuringiensis subsp. kurstaki HD-1-Dipel with [32P]orthophosphate at different stages of growth and differentiation. Marked changes in the profile of phosphopolypeptides were observed primarily during the late exponential phase of growth. Several phosphopolypeptides co-purified with the endotoxin crystal of this subspecies and the phosphoamino acid residue of the most abundant (Mr 25,000) phosphopolypeptide was identified as phosphothreonine. Comparison of the phosphopolypeptides in endotoxin crystals from several subspecies suggested that Mr 25,000 species might be a common component.