Structure-Function Analysis of Staphylococcus aureus Amidase Reveals the Determinants of Peptidoglycan Recognition and Cleavage

Abstract

Background: Autolysins ensure the plasticity of bacterial cell walls, and deletion leads to impaired cell clusters. Results: High resolution structures of Staphylococcus aureus amidase AmiA shed light on peptidoglycan binding and cleavage. Conclusion: AmiA distinguishes peptidoglycan mostly by the peptide, and cleavage is facilitated by a zinc-activated water molecule. Significance: These structures will inform strategies to develop new therapeutics against MRSA.

The crystal structure of the major pneumococcal autolysin LytA in complex with a large peptidoglycan fragment reveals the pivotal role of glycans for lytic activity

“…B). These new orientations of the two catalytic residues Glu87 and His147 agree well with the reaction mechanism previously suggested by us and others in which Glu87 and the Zn 2+ ion polarize the scissile bond (Zoll et al ., ; Buttner et al ., ; Mellroth et al ., ).…”

X-ray crystallography and its impact on understanding bacterial cell wall remodeling processes

“…Investigation of the closely related AmiA from S. aureus led to the identification of a dense interaction network between enzyme and substrate, and subsequently the specificity as well as a plausible reaction mechanism (Büttner et al, 2014). Since the participating residues are highly conserved, this mechanism likely is used by all Amidase 2 enzymes (Büttner et al, 2014;Paget et al, 1999).…”

“…The groove is also bordered by a loop and harbors the three zinc-binding as well as catalytically and structurally stabilizing residues. The catalytic zinc ion is typically coordinated by histidines 265 and 370 (numbering and described interactions according to AmiA (Büttner et al, 2014) for whole Amidase 2 section) and aspartic acid 384 (Fig. 2B).…”

“…3C shows the enzyme-substrate complex of AmiA (4KNL, (Büttner et al, 2014)). A dense network of direct and water-mediated interactions orients the peptide stem of PGN within the narrow, elongated AmiA binding groove.…”

“…2C). The carbonyl oxygen of alanine 266 likely stabilizes an intermediate state during catalysis, analogous to aspartate 266 of AmiA (Büttner et al, 2014). Asparagine or aspartate 267 are well positioned to engage contacts with MurNAc, again analogous to threonine 267 of AmiA.…”