Characterization of the dicyclohexylcarbodiimide-binding protein isolated from chloroplast membranes.

Characterization of a butanol-solubilized protein isolated from chloroplast membranes is reported. The proteolipid, which specifically and covalently binds dicyclohexylcarbodiimide, has an apparent molecular weight of 8,000 in dodecylsulfate electrophoresis. The minimum molecular weight calculated from amino acid analysis data is 7,700. N-Formyl-methionine was determined to be the N-terminal amino acid. Glycine, alanine and leucine were present in elevated amounts, resulting in a polarity of 29%. Cysteine and histidine were lacking. In high-voltage electrophoresis the peptide appeared as a single homogenous spot which migrated, at pH 6.5, with the relative mobility of glycine. At concentrations where dicyclohexylcarbodiimide inhibited ATPase activity maximally (20 nmol per mg membrane protein), 0.17 nmol dicyclohexylcarbodiimide was covalently bound per nmol isolated proteolipid, indicating that one out of six molecules of proteolipid was labeled.