Subcellular Location of the Soluble Lytic Transglycosylase Homologue in Staphylococcus aureus

Abstract

The immunodominant antigen A, IsaA, of Staphylococcus aureus was found to include a putative soluble lytic transglycosylase domain in its C-terminal region. Since the presence of this distinctive domain suggested that the protein might participate in peptidoglycan turnover, as indicated in Gram-negative bacteria, its cellular location was investigated. The protein was found not only in the culture supernatant but also in the cell wall fraction. To estimate its physiological role for the bacterium, its cell surface distribution was studied by immunoelectron microscopy. Protein A-gold particles binding to the immune complex were mainly located on the septal region of the bacterial cell surface. These data suggested that IsaA might be involved in bacterial cell separation through a preferential interaction with peptidoglycan chain.

Characterization of IsaA and SceD, Two Putative Lytic Transglycosylases of Staphylococcus aureus

“…One of the antigens identified was a putative autolysin, IsaA (immunodominant staphylococcal antigen; SACOL2584) (51). This was in agreement with a previous study identifying IsaA as a major antigen of S. aureus (39).…”

“…Cellular fractionation and SDS-PAGE of an S. aureus SH1000 (wild-type) culture revealed that IsaA is a major protein ionically bound to the cell wall ( Fig. 1) and in the culture supernatant (results not shown), as has been shown previously (51). In order to facilitate the study of IsaA, an allelic replacement mutation was generated, creating strain MS001 (isaA), which was verified by Southern blotting (results not shown).…”

Relative Quantitative Comparisons of the Extracellular Protein Profiles ofStaphylococcus aureusUAMS-1 and ItssarA,agr, andsarA agrRegulatory Mutants Using One-Dimensional Polyacrylamide Gel Electrophoresis and Nanocapillary Liquid Chromatography Coupled with Tandem Mass Spectrometry

“…A second protein (Q6GED5) was originally identified as an immunodominant staphylococcal antigen (IsaA) reactive with antisera taken from patients with MRSA sepsis (39). This protein was later shown to have a C-terminal domain with sequence similarity to the soluble lytic transglycosylase (Slt70) of Escherichia coli and found in spent media but also in the cell wall, primarily within the septal region of the cell (52).…”

Different subcellular locations of secretome components of Gram-positive bacteria

“…The non-covalently cellwall-bound lytic transglycosylase IsaA of Staph. aureus is also mainly present in the septal region of dividing cells, and thus is possibly secreted at this site (Sakata et al, 2005). It therefore appears to be a common characteristic for many non-covalently cell-wall-bound proteins that they are secreted at the site of cell wall binding, where their biological activity may be needed.…”