Repetitive Sequences in Protein A from Staphylococcus aureus

After tryptic digestion of intact Staphylococcus aureus the residual portion of protein A that was still bound to the cell wall was cleaved off with lysostaphin. From the two digests Fc-binding fragments were isolated and the following characteristics observed. (a) There are four Fc-binding, highly homologous regions, each consisting of 58--62 amino acid residues. (b) These regions are consecutively arranged from the N-terminal part of the protein. (c) The residual C-terminal part, approximately 150-residues long, differs to a great extent with respect to primary and secondary structures from the four active regions. Furthermore, it is suggested that the protein is bound to the bacterial cell wall structure through this C-terminal part.