Hemolytic streptococci cell proteins

Most bacterial cells are characterized by a tough, rigid cell wall (31). In some instances it is possible to isolate proteins from the cell surface or interior by simple extraction procedures without first breaking the cell wall. Thus M" protein can be extracted from hemolytic streptococci with i T/20 hydrochloric acid at 37°C. (Lancefield, 75) and T protein by treatment of the cells with pepsin at pH 2.5 for 6-12 hours (Lancefield and Dole, 78). Although some chemical alteration may be caused by such rather drastic procedures, M and T proteins extracted in this manner exhibit serological behavior similar to that shown in the intact cell. 

The antigenic structure of hemolytic streptococci has been extensively studied by Lancefield and her coworkers (76). It has been shown that at least two type-specific antigenic components, both probably protein in nature, are concerned with the type-specific reactions of group A hemolytic streptococci. These components have been designated M and T. In addition, the cells contain at least one species-specific protein capable of cross-reacting with pneumococci, which has been designated P (76, 144). 

M Protein of Hemolytic Streptococcus Group A. The experiments of Olarte referred to have now been published (154). Olarte has demonstrated that as much M protein may be recovered from the culture nitrates of certain strains of group A hemolytic streptococci as may be extracted by the Lancefield technique from the cells themselves. M protein from the culture filtrate may be fractionated by ammonium sulfate precipitation. Partially purified M protein prepared in this way did not prove to be a better antigen than material extracted from the cells at 37°C. with acid by the technique of Hirst and Lancefield loc. cit.) as had been hoped. There appears to be a correlation between mouse virulence and release of extracellular M protein. Only those strains which retain the M protein on the cell surface and do not release it into the supernatant are virulent for mice,... 

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