Characterization of the Modular Design of the Autolysin/Adhesin Aaa from Staphylococcus Aureus

Abstract

Background Staphylococcus aureus is a frequent cause of serious and life-threatening infections, such as endocarditis, osteomyelitis, pneumonia, and sepsis. Its adherence to various host structures is crucial for the establishment of diseases. Adherence may be mediated by a variety of adhesins, among them the autolysin/adhesins Atl and Aaa. Aaa is composed of three N-terminal repeated sequences homologous to a lysin motif (LysM) that can confer cell wall attachment and a C-terminally located cysteine, histidine-dependent amidohydrolase/peptidase (CHAP) domain having bacteriolytic activity in many proteins. Methodology/Principal Findings Here, we show by surface plasmon resonance that the LysM domain binds to fibrinogen, fibronectin, and vitronectin respresenting a novel adhesive function for this domain. Moreover, we demonstrated that the CHAP domain not only mediates the bacteriolytic activity, but also adherence to fibrinogen, fibronectin, and vitronectin, thus demonstrating for the first time an adhesive function for this domain. Adherence of an S. aureus aaa mutant and the complemented aaa mutant is slightly decreased and increased, respectively, to vitronectin, but not to fibrinogen and fibronectin, which might at least in part result from an increased expression of atl in the aaa mutant. Furthermore, an S. aureus atl mutant that showed enhanced adherence to fibrinogen, fibronectin, and endothelial cells also demonstrated increased aaa expression and production of Aaa. Thus, the redundant functions of Aaa and Atl might at least in part be interchangeable. Lastly, RT-PCR and zymographic analysis revealed that aaa is negatively regulated by the global virulence gene regulators agr and SarA. Conclusions/Significance We identified novel functions for two widely distributed protein domains, LysM and CHAP, i.e. the adherence to the extracellular matrix proteins fibrinogen, fibronectin, and vitronectin. The adhesive properties of Aaa might promote S. aureus colonization of host extracellular matrix and tissue, suggesting a role for Aaa in the pathogenesis of S. aureus infections.

The adhesive properties of the Staphylococcus lugdunensis multifunctional autolysin AtlL and its role in biofilm formation and internalization

“…S. epidermidis AtlE and the homologous S. aureus AtlA were reported to be responsible for attachment of bacterial cells to a polymer surface and to bind also to ECM proteins, thereby representing an initial step in biofilm formation (Heilmann et al, 1997). Two homologous 35-kDa surface-associated autolysins/adhesins in S. epidermidis (Aae) (Heilmann et al, 2003) and S. aureus (Aaa) (Heilmann et al, 2005;Hirschhausen et al, 2012) also bind to Fg, Fn, and Vn. In this study, we report the pivotal role of AtlL in adherence and biofilm Fig.…”

Coagulase-Negative Staphylococci

“…The major 148-kDa surface-associated autolysin/adhesin, AtlE, from S. epidermidis mediates initial adherence of bacterial cells to the polymer surface and is highly similar to the S. aureus autolysin Atl (239). AtlE and Atl are organized in the same modular structure and are functionally interchangeable (239,240). AtlE is proteolytically cleaved into two bacteriolytically active domains: a 60-kDa amidase (AM) and a 52-kDa glucosaminidase (GL).…”

Important Contribution of the Novel Locus comEB to Extracellular DNA-Dependent Staphylococcus lugdunensis Biofilm Formation

“…4B, lower). Moreover, no significantly differential expression of the atlL (SLUG_18190; available at the KEGG database [http://www.genome.ad.jp/kegg/]) and aal (SLUG_01420; available at the KEGG database) genes, encoding the autolysins AtlL and Aal, which are homologous to the major autolysins AtlA and Aaa from S. aureus (49,50) and AtlE and Aae from S. epidermidis (38,51), respectively, was detected by real-time PCR (Fig. 4C).…”