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Biomedical subjects

M McCarty

Publications and source records attributed to M McCarty.

At least 73 records · Page 4Linked to original sources
PubMed1979

Characterization and localization of the enzymatic deacylation of lipoteichoic acid in group A streptococci.

Protoplasts of a group A streptococcal strain were shown to contain enzymatic activity capable of converting lipoteichoic acid (LTA) to deacylated lipoteichoic acid (dLTA). The enzyme(s) appear to be located mainly in the membrane, although activity was also found in the cytoplasm. Determination of the sites of cleavage within the LTA molecule was approached by comparing the chemical composition of LTA and native dLTA. Native dLTA, as distinguished from chemically deacylated LTA, was isolated from buffer in which live streptococci had been resuspended and incubated. The chemical data suggest that the enzyme(s) was(were) lipolytic in nature; that is, the conversion of LTA to dLTA was the result of cleavage of the ester linkages between the fatty acids and the remainder of the LTA molecule.

Carboxylic Ester Hydrolases↗
PubMed1979

Amino acid sequence and physicochemical similarities between streptococcal M protein and mammalian tropomyosin.

The amino-terminal sequences of two peptides of type 24 streptococcal M protein show similarities with that of rabbit skeletal muscle tropomyosin, having up to 40% identical residues and probabilities of occurring by chance as low as P less than 10(-5). In addition, a hexapeptide (Glu-Ala-Glu-Lys-Ala-Ala) that is found five times in the M24 protein was shown to be identical to a sequence in tropomyosin. Similarities are also seen in the amino acid compositions and physicochemical properties of the two proteins. The amino-terminal sequences of peptides from another bacterial surface protein, staphylococcal protein A, are highly correlated with segments of two other myofibrillar proteins, rabbit actin (P less than 10(-7)) and rabbit myosin A1 light chain (P less than 10(-6)). The data presented suggest that a close structural relationship exists between mammalian muscle proteins and the biologically active surface proteins of staphylococci and streptococci. In addition, the correlation between sequences in M protein and tropomyosin represents direct evidence of a structural similarity at a molecular level between a streptococcal protein and a mammalian muscle component and may therefore prove relevant to the pathogenicity of the streptococcus.

Actins↗
PubMed1977

Group A streptococcal antigens cross-reactive with myocardium. Purification of heart-reactive antibody and isolation and characterization of the streptococcal antigen.

Heart-reactive antibody (HRA) appears in the sera of experimental animals inoculated with group A streptococci as well as patients with acute rheumatic fever. Adsorption of either serum with group A streptococcal membranes will remove the HRA. Blocking experiments between these two types of HRAs have demonstrated that the antibodies are directed towards different antigenic determinants on either the same or different molecules. To isolate and purify the antigen from the group A streptococcus cross-reactive with sarcolemmal sheaths of cardiac myofibers, it became necessary to purify the HRA from rheumatic fever patients' sera. Isolated gamma globulin containing all of the HRA was adsorbed onto human sarcolemmal sheaths. The specific HRA was released by using potassium iodide. Over 99 percent of the purified HRA was shown to bind the sarcolemmal sheath whereas less than 1 percent of the antibody would bind nonspecifically to other material. Preparations of group A streptococcal membrane will bind HRA purified from the sera of acute rheumatic patients at levels of 97 percent or greater. The cross-reactive antigen solubilized by nonionic detergent was purified 120-fold by column chromatography. On sodium dodecyl sulfate polyacrylamide electrophoresis, the antigen was demonstrated to be composed of four polypeptides with mol wt of 32,000, 28,000, 26,000, and 22,000 daltons, respectively. Only proteolytic enzymes could destroy the antigenic determinant whereas glycosidases and lipases had no effect. The purified antigen blocked the binding of purified HRA to normal human heart sections.

Animals↗
PubMed1977

Teichoic acids of group D streptococci with special reference to strains from pig meningitis (Streptococcus suis).

Immunoelectrophoresis revealed in phenol extracts from S. faecalis and S. faecium a mixture of free and lipid-bound teichoic acids, both reactive with Group D antisera. In phenol extracts from S. suis only lipid-bound teichoic acid, also reactive with Group D antiserum, was seen. This difference probably accounts for the low yield of Group D antigen from S. suis as compared with S. faecalis and S. faecium when heating at pH 2 is used for extraction. When phenol is used good yields are obtained from S. suis as well as from S. faecalis and S. faecium. Lipoteichoic acids from S. faecalis and S. faecium have a backbone structure the same as or similar to that of Group A streptococcal teichoic acid. Lipoteichoic acid from S. suis has a structure differing from that of S. faecalis and S. faecium, e.g., possibly in the attachment of its glucosyl substituents. Precipitation reactions between S. suis lipoteichoic acid and Group D antisera were specifically inhibited by glucose. Reactions between S. bovis phenol extracts and some Group D antisera were also specifically inhibited by glucose, but extracts from S. faecalis and S. faecium were not. This may indicate a monosaccharide glucosyl substituent in teichoic acid from S. suis and S. bovis instead of the di- or trisaccharide previously postulated as the glucosyl substituent in the teichoic acid of S. faecalis.

Animals↗
PubMed1975

Multiple mouse-protective antibodies directed against group B streptococci. Special reference to antibodies effective against protein antigens.

The data presented in this paper establish the finding that multiple specific protective antibodies exist in rabbits in response to immunization with Group B streptococci. The summary in Table I indicates the serological types into which Group B streptococci have been divided on the basis of their antigenic composition. This classification is dependent upon passive protection of mice with antibodies directed against the specific antigens, and types are defined in these terms. Heretofore, it was thought that type-specific polysaccharides accounted for all such protection in Group B streptococci. Certain exceptions of cross-protection between types due to minor polysaccharide determinants soon appeared; cross-protection reactions based on protein determinants in at least two types were also discovered. The present experiments show that specific antibodies directed to either polysaccharide or protein antigens of a single strain can be protective against infection with streptococci containing these antigens.

Absorption↗
PubMed1975

The Dalkon Shield controversy. Structural and bacteriological studies of IUD tails.

The recent report of 209 cases of septic spontaneous abortion and 11 maternal deaths in the United States in women using the Dalkon Shield intrauterine device (IUD) raised the question about a possible causal relationship between the IUD and pelvic sepsis. It is essential to determine whether or not this sipsis is unique to the Dalkon Shield or generic to all types of IUDs. Our studies permit the conclusion that the tail of the Dalkon Shield is structurally and functionally different from the tails of the four other IUDs tested. The unique characteristics of the Dalkon tail theoretically could provide a mechanism whereby pathogenic bacteria from the vagina enter the uterine cavity and cause sepsis.

Abortion, Septic↗
PubMed1969

Electron microscopic studies on opaque colony variants of group A streptococci.

Opaque colony variants of two strains of group A streptococci have been compared with blue colonies of the same strains by electron microscopy. In opaque colonies, the cocci are joined into elongated chains by exaggerated intercellular septa that often occupy the major portion of each cell's circumference. The thickness and lamination of cell walls in opaque colony variants are identical to those aspects of cell walls in blue colony forms. The similarity in cell wall architecture is found between opaque and blue forms whether or not M protein (and M associated surface fimbriae) is present. Extensive, direct contact between the nucleoid and the cytoplasmic membrane beneath intercellular septa is seen in opaque colony variants. The relationship of this marked nucleoid-cytoplasmic membrane association to the unusual chain forms in the opaque colony variants is unclear.

Cell Membrane↗
PubMed1968

Intraphagocytic beta-N-acetylglucosaminidase. Properties of the enzyme and its activity on group A streptococcal carbohydrate in comparison with a soil bacillus enzyme.

The beta-N-acetylglucosaminidases of rabbit and human polymorphonuclear leukocytes and of rabbit alveolar macrophages have been studied in comparison with the beta-N-acetylglucosaminidase derived from a soil bacillus which had previously been shown to hydrolyze the group-specific polysaccharide of Group A streptococci. The phagocytic enzymes are lysosome associated and have an acid pH optimum. In contrast, the soil bacillus enzyme is an extracellular product, has a higher pH optimum, and is probaby of smaller molecular size. When tested on p-nitrophenyl-betaN-acetylglucosaminide as substrate, the K(m) of the phagocytic enzymes is slightly higher than that of the soil bacillus. However, there were extreme differences in their effect on the Group A streptococcal polysaccharide. Thus, 5 x 10(6) units of the alveolar macrophage enzyme were required to hydrolyze the available N-acetylglucosamine of 1 mg of polysaccharide in 18 hr, while 100 units of the soil bacillus enzyme were sufficient to achieve this hydrolysis. In both cases, the serological reactivity of the polysaccharide is altered with loss of Group A specificity and acquisition of a new specificity characteristic of A-variant streptococci. Possible explanations for differences in the activity of the enzymes are considered, and the role of the phagocytic enzymes in intracellular degradation of Group A streptococci is discussed.

Animals↗