Size variation of the M protein in group A streptococci.

Abstract

Streptococcal M protein, the fibrillar molecule on the surface of the group A streptococcus, is considered to be one of the major factors responsible for the ability of this human pathogen to cause disease (1). Though type-specific opsonic antibodies directed towards the M molecule enable the infected host to clear the invading streptococcus (1, 2), the ability of this organism to vary its antigenic structure has probably been the major factor responsible for its survival. To date, over 75 serologically different M proteins have been identified in nature along with an increasing number of nontypable strains isolated from infected individuals (World Health Organization Conference, 1984, Tokyo, Japan).Based on structural and physicochemical studies, it appears that the M protein is composed of two predominantly alpha-helical protein chains assembled in a coiled-coil (3-5) and extending nearly 600 A. from the cell surface (5). Partial sequence analysis of three different M molecules has revealed that these sequences are essentially different, but have a common placement of hydrophobic residues (4, 6, 7) that is responsible for maintaining the coiled-coil structure (4, 5) common to those M molecules studied. Though many of these studies have been useful in understanding the structure and immunochemistry of the M molecule, they have been primarily confined to an amino-terminal fragment of the protein comprising nearly half the molecule (pepsin-extracted M protein) (4, 6, 7).Several different procedures for obtaining M protein from whole streptococci or their isolated cell walls have been used, including extraction with acid (8), alkali (9), pepsin (10, 11), and nonionic detergent (12). In all cases, however, the resulting product was probably a fragment of the native molecule. Despite some attempts to isolate the M protein from the streptococcus with cell wail-solubilizing enzymes (13-16), the complexity of the resulting digest has offered little information about the nature of the native molecule as it exists on the streptococcus. To avoid the destructive properties of certain extraction techniques, M protein was purified from the secreted products of streptococcal L forms and protoplasts of type 12 streptococci (17). The molecular weight of the M protein monomer from these two sources was 58,000. In more recent studies, Scott and Fischetti (18) cloned the gene for M6 in Escherichia coli, and Fischetti et al. (19)

Demonstration of peptidoglycan-associated Brucella outer-membrane proteins by use of monoclonal antibodies

“…PG-associated OMPs would be released by lysozyme treatment, with one, two, etc., murein subunits remaining attached, giving them an increasingly lower electrophoretic mobility. Similar phenomena have also been described for other Gram-negative bacteria, including Braun's lipoprotein of E. coli (Wensink & Witholt,198 1) and the major OMPs of Rhizobium leguminosarum (de Maagd et al, 1989a, b) and Legionella pneumophila (Butler & Hoffman, 1990) and for the M protein of group A streptococci (Fischetti et al, 1985;Pancholi & Fischetti, 1988). The high-molecular-mass bands in immunoblots of lysozyme-treated sonicated cell extracts, ranging from 50 to 54 kDa reacting with the anti-25-27 kDa mAb, 54 to 66 kDa with the anti-31-34 kDa mAb and 78 kDa with the anti-36-38 kDa mAb, probably represent dimeric forms of each major OMP where the monomers are linked together by PG.…”

Mry, a trans-acting positive regulator of the M protein gene of Streptococcus pyogenes with similarity to the receptor proteins of two-component regulatory systems

“…E. coli DH5a was grown in Luria broth (32) or tryptone (32), and S. pyogenes strains were grown in ToddHewitt broth supplemented with 0.2% yeast extract (THY) (11). Antibiotics were used at the following concentrations: ampicillin (Ap) at 50 ,ug/ml, chloramphenicol (Cm) at 10 ,ug/ml for E. coli and 5 ,ug/ml for S. pyogenes, kanamycin (Km) at 25 ,ug/ml for E. coli and 200 ,ug/ml for S. pyogenes, and streptomycin at 1,000 ,ug/ml for S. pyogenes.…”

PlyC: A multimeric bacteriophage lysin

“…Consequently, this enzyme has been used as a molecular tool for decades to isolate cell-wall-linked proteins and extract DNA from group A streptococci (9,10). More recently, we have shown that the bacteriolytic properties of PlyC can protect mice from streptococcal challenge, suggesting a therapeutic use of the enzyme (11).…”