Two Allelic Forms of the Aureolysin Gene ( aur ) within Staphylococcus aureus

Abstract

Proteinases of Staphylococcus aureus are emerging as potential virulence factors which may be involved in the pathogenecity of staphylococcal diseases. We describe here the structure of the gene encoding the metalloproteinase referred to as aureolysin. This gene occurs in two allelic forms and is strongly conserved among S. aureus strains, implying the possibility that the proteinase may have important housekeeping functions.Staphylococcus aureus is a major human pathogen of increasing importance because of its rapid development of antibiotic resistance. Due to the possession of a broad array of potential virulence factors, including several toxins, adhesins, and exoenzymes, this organism is able to colonize a broad range of tissues in the host and, as a result, cause many grave infections (9). Recently, a renewed interest has been focused on proteinases from S. aureus which are under the control of agr (accessory gene regulator) and sar (staphylococcal accessory regulator), the main regulators of S. aureus virulence determinant genes (3,4,8). In this case, the expression of a specific serine glutamyl endopeptidase (V8 protease) was found to be important for the full display of bacterial virulence in animal models of staphylococcal infection (5).In addition to the glutamyl endopeptidase, S. aureus secretes at least one papain-like cysteine proteinase as well as a typical metalloproteinase that is commonly referred to as aureolysin. The primary and tertiary structures of the latter enzyme have been determined (1), revealing a polypeptide chain of 301 amino acids which is folded into a ␤-pleated N-terminal domain and an ␣-helical C-terminal domain, a typical fold for the thermolysin family of metalloproteinases. This diverse family of proteinases also encompasses several enzymes which are acknowledged virulence factors, including Pseudomonas aeruginosa elastase, Legionella pneumophila and Listeria monocytogenes metalloproteinases, Vibrio cholerae hemagglutinin protease, Staphylococcus epidermidis elastase, and the lambda toxin of Clostridium perfringens. In contrast to these proteinases, however, little is known about the exact role of aureolysin in the pathogenicity of S. aureus. In vitro, aureolysin has been shown to cleave the plasma proteinase inhibitors, ␣ 1 -antichymotrypsin and ␣ 1 -proteinase inhibitor (13,14), and to activate prothrombin in human plasma (20). It may also affect the stimulation of T and B lymphocytes by polyclonal activators and display inhibitory activity against immunoglobulin production by lymphocytes (15). In addition, aureolysin activates the precursor of the glutamyl endopeptidase (V8 protease) secreted by this same microorganism (6).In order to cast more light on the potential importance of staphylococcal proteinases in pathogenicity, we have focused the present study on the genetic analysis of aureolysin, including distribution, copy number, and genetic variability of the aureolysin gene in both clinical isolates and laboratory strains of S. aureus.The PCR technique was first appli...

The role and regulation of the extracellular proteases of Staphylococcus aureus

“…Of the four major extracellular proteases secreted by S. aureus, the loci encoding Aur, SspA and SspB have previously been identified (Sabat et al, 2000;Rice et al, 2001). However, the staphopain-encoding region has yet to be identified.…”

“…SspB is also found as a proteolytically processed product in culture supernatants, and it is proposed that SspA is the agent responsible for this cleavage Rice et al, 2001). Characterization of the gene encoding Aur (Sabat et al, 2000) uncovered a putative ORF of 1530 bp, with a resultant gene product of 509 aa. Crystal structure (Banbula et al, 1998) and N-terminal analysis have revealed that mature Aur is only 301 aa long, indicating the need for posttranslational processing.…”

Identification of a Novel Maturation Mechanism and Restricted Substrate Specificity for the SspB Cysteine Protease ofStaphylococcus aureus

“…The SspA serine protease is itself expressed as an inactive zymogen that is activated by a metalloprotease aureolysin (10), which also exhibits an N-terminal propeptide and C-terminal catalytic domain (32). Although the mechanism for aureolysin maturation has not been elucidated, these steps define a pathway in which maturation of the SspB cysteine protease requires the sequential activity of metalloproteases and serine proteases.…”

Comparative Genomics of Staphylococcus aureus Musculoskeletal Isolates

“…This suggests that these strains encode an allelic variant by comparison to the strains used to generate the PFGRC array. Indeed, Sabat et al (57) previously reported the existence of aur allelic variants, and the Affymetrix GeneChip includes a second aur allele that was indeed present in UAMS-1, UAMS-601, and EMRSA-16. Similarly, the coagulase gene (COL-SA0209) was classified as absent in UAMS-1, UAMS-601, EMRSA-16, and SANGER-476 based on the PFGRC arrays, which included only one coa allele.…”