Detection and purification of a potential precursor protein or a prohaemolysin produced by Staphylococcus haemolyticus.

The haemolytic substance H7 produced by Staphylococcus haemolyticus is composed of three peptides out of 44 amino acid residues each having a structure resembling a signal peptide. The cytoplasmic fraction for the presence of a protein precursor containing this signal sequence was investigated. Specific rabbit IgGs to substance H7 were isolated by affinity chromatography on Sepharose-4B-H7. These anti-H7 IgGs recognized mainly a 51 kD protein in the cytoplasmic fraction of S. haemolyticus from 2, 4, 6, 8, 10 and 23 h cultures. These results support the idea that the 51 kD protein could be either a prohaemolysin or else the precursor of a protein of unknown function with a signal sequence showing homology with the haemolytic peptides. After affinity chromatography on Sepharose-4B-anti-H7, the 51 kD protein was shown associated with an RNA-protein complex composed of four or five proteins and an RNA estimated at 300 nt. This complex could be associated with the machinery of protein secretion. The 51 kD protein was finally purified to homogeneity by HPLC on a Protein Pak DEAE-5PW column in the presence of 5 M urea.