Involvement of Acyl Carrier Protein in Acylation of Glycerol 3-Phosphate in Clostridium butyricum

Clostridium butyricum grown in medium supplemented with radioactive pantothenic acid incorporates this compound into both protein and nonprotein fractions of the cell. Acyl carrier protein (ACP) is the major protein into which pantothenic acid is incorporated. C. butyricum ACP was isolated as a homogeneous protein, as judged by column chromatography on DEAE-Sephadex, disc gel electrophoresis, and analytical ultracentrifugation. This protein contains a single sulfhydryl residue, 2-mercaptoethylamine, which is a component of the prosthetic group, 4'-phosphopantetheine. The prosthetic group is cleaved from the protein when the protein is incubated at pH 12, 70°, for 1 hour. Although this protein has properties similar to those of ACP of Escherichia coli, the amino acid compositions of the two proteins are different. The chemical synthesis of long chain fatty acyl-ACP derivatives is described. In this procedure other unidentified groups of the protein are acylated as well as the sulfhydryl group. The effects of acylation or acylation and alkylation of groups other than the sulfhydryl group of ACP were studied by testing ACP regenerated from such derivatives in the malonyl coenzyme A-CO2 exchange reaction.