Proteolytic digestion of the micellar complex of f1 coat protein and deoxycholate

The major coat protein of bacteriophage f1 radioactively labeled with specific amino acids was solubilized with deoxycholate and digested with trypsin or alpha-chymotrypsin. The degree of proteolysis of the coat protein was assayed by gel filtration chromatography of the digest in the presence of deoxycholate. Hydrolysis occurred at residues in the hydrophilic termini of the coat, releasing peptides containing proline, lysine, and phenylalanine. No cleavage occurred at the tyrosine or methionine residues in the hydrophobic core. However, chymotrypsin could cleave somewhat at these residues in the absence of deoxycholate. A model for the topography of the micellar complex of coat protein and deoxycholate is presented in which the hydrophobic sequence of the coat is bound to deoxycholate within a micelle, while the hydrophilic termini of the coat project from the micelle.