Some Physicochemical Properties of Protein A from <i>Staphylococcus aureus</i>

To study the active site(s) in protein A, partial tryptic digestions of the protein and of intact Staphylococcus aureus were performed. Fragments which bind to the Fc‐part of human IgG were isolated by affinity chromatography on IgG‐Sepharose 4B and purified by ion‐exchange chromatography on phosphocellulose. From a partial tryptic digest of pure protein A at 30°C, pH 8.2 for 30 min we have isolated and characterized six active fragments with molecular weights ranging from 6000 to 8000. Two active fragments, obtained in high yields by digestion at pH 7.2 of intact protein‐A‐containing bacteria, were shown to be similar to two of the six characterized fragments from the digest of pure protein A. All fragments appeared to have similar amino acid sequences, judged by peptide mapping, specific staining and amino acid analysis; some are very possibly overlapping peptides. Each fragment probably contains only one active site region since all are monovalent in the Fc‐reaction when studied with a hemagglutination technique. The maximal molar yield of active fragments obtained from the digestion of pure protein A accounts for about 210% of the amount of protein A used. Thus protein A, suggested to consist of repeating units, should exhibit at least three similar if not identical active regions.

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“…Staphylococcal protein A is another bacterial surface protein that resembles M protein in antiphagocytic activity (32), amino acid composition (33), extended shape (34), and internally repetitive sequences (33,35). Protein A is composed of four highly homologous regions, each consisting of 58 amino acid residues, which are capable of binding the Fc region of IgG (35).…”

mentioning

confidence: 99%

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

Hosein¹,

McCarty²,

Fischetti³

1979

Proc. Natl. Acad. Sci. U.S.A.

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ABSTRACr-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 < 10-5. In addition, a hexapeptide (Glu-Ala-Glu-Lys-AlaAla) 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 tfie 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 < 10-7) and rabbit myosin Al light chain (P < 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.Group A streptococci possess antiphagocytic surface antigens, known as M proteins, that are primarily responsible for the virulence of these organisms (1). Based on extensive immunological data, it has been clearly shown that resistance to streptococcal infection is dependent on neutralization of the antiphagocytic effect of M proteins by type-specific opsonic antibodies (1, 2). Immunological cross reactions do occur' between certain of the more than 70 immunologically distinct M types (3, 4), but the antibodies involved rarely afford crossprotection (3). Recent peptide analyses (5) and sequence studies (6, 7) on a limited number of M protein types revealed that, in spite of a common biological activity, M proteins are composed of different primary structures. Despite these immunological and structural differences, all M protein molecules studied to date share certain noteworthy chemical and physical properties (8). Their extreme thermal stability (9), their highly elongated shape (10, 11), and their appearance as a network of projections on streptococcal cell walls (12) suggested that M proteins might have properties in common with previously characterized fibrous proteins.This report describes striking chemical, physical, and sequence similarities between streptococcal M protein and rabbit skeletal muscle tropomyosin. In addition, computer analysis of the partial sequence of staphylococcal protein A, another biologically active, Gram-positive, surface protein, having properties in common with M protein, reveals significant homology with two other myofibrillar proteins, actin and myosin Al light chain.

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Some Physicochemical Properties of Protein A from Staphylococcus aureus

Cited by 213 publications

References 21 publications

Repetitive sequences in protein a from Staphyloccus aureus: Three highly homologous Fc‐binding regions

Repetitive sequences in protein a from Staphyloccus aureus: Three highly homologous Fc‐binding regions

Immunologically Active and Structurally Similar Fragments of Protein A from Staphylococcus aureus

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

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