Physico‐ and Immunochemical Properties of Staphylococcal Protein A Extracellularly Produced by a Set of Mutants from Staphylococcus aureus Cowan I

Mutant strains of Staphylococcus aureus have been isloated using a simple cosedimentation technique. While the parental strain contains predominantly a cell-bound protein A, the mutant strains exclusively produce extracellular protein A. The mutant forms of protein A all have lower molecular weights than that of protein A from the parental strain. They showed the same antigenicity as the parental protein A and gave similar reactivity with immunoglobulin to the parental one except for one mutant. A conspicuous spur was observed between the parental protein A and that produced by the mutant against normal dog serum in the micro-Ouchterlony immunodiffusion test.