Understanding the Structure–Function Relationship of Lysozyme Resistance in Staphylococcus aureus by Peptidoglycan O-Acetylation Using Molecular Docking, Dynamics, and Lysis Assay

Abstract

Lysozyme is an important component of the host innate defense system. It cleaves the β-1,4 glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine of bacterial peptidoglycan and induce bacterial lysis. Staphylococcus aureus (S. aureus), an opportunistic commensal pathogen, is highly resistant to lysozyme, because of the O-acetylation of peptidoglycan by O-acetyl transferase (oatA). To understand the structure-function relationship of lysozyme resistance in S. aureus by peptidoglycan O-acetylation, we adapted an integrated approach to (i) understand the effect of lysozyme on the growth of S. aureus parental and the oatA mutant strain, (ii) study the lysozyme induced lysis of exponentially grown and stationary phase of both the S. aureus parental and oatA mutant strain, (iii) investigate the dynamic interaction mechanism between normal (de-O-acetylated) and O-acetylated peptidoglycan substrate in complex with lysozyme using molecular docking and molecular dynamics simulations, and (iv) quantify lysozyme resistance of S. aureus parental and the oatA mutant in different human biological fluids. The results indicated for the first time that the active site cleft of lysozyme binding with O-acetylated peptidoglycan in S. aureus was sterically hindered and the structural stability was higher for the lysozyme in complex with normal peptidoglycan. This could have conferred reduced survival of the S. aureus oatA mutant in different human biological fluids. Consistent with this computational analysis, the experimental data confirmed decrease in the growth, lysozyme induced lysis, and lysozyme resistance, due to peptidoglycan O-acetylation in S. aureus.

Genetic Determinants Enabling Medium-Dependent Adaptation to Nafcillin in Methicillin-Resistant Staphylococcus aureus

“…These results are consistent with previous data showing that exposure of MRSA to methicillin results not only in reduced peptidoglycan cross-linking but also in reduced peptidoglycan O-acetylation (63). O-acetylation is important for resisting autolysis activity from lysozymes (64) and has been shown to increase susceptibility to certain ␤-lactams (65). Reduction in O-acetylation has great implications for the host-pathogen relationship in S. aureus infections.…”

Baicalin promotes the bacteriostatic activity of lysozyme on S. aureus in mammary glands and neutrophilic granulocytes in mice

“…Indeed, LYSO contributes to surveillance of mammalian cells membranes, fortification of the phagocytic activity of neutrophils and macrophages [7], and secretion by polymorphonuclear leukocytes [8]. LYSO breaks bacterial cell walls via hydrolysis of peptidoglycan [9] and is thus particularly effective against Gram-positive bacteria. It is extensively used in the pharmaceutical and food industries due to its anti-inflammatory, anti-viral, immune modulatory, anti-histaminic and anti-tumor effects [10].…”

Role of the msaABCR Operon in Cell Wall Biosynthesis, Autolysis, Integrity, and Antibiotic Resistance in Staphylococcus aureus

“…Briefly, overnight cultures of S. aureus strains were pelleted, washed twice with ice-cold PBS, and suspended in buffer containing 350 g/ml of lysozyme. The initial OD 600 was adjusted to 0.8, and the decrease in OD 600 was measured at hourly intervals for 6 h and finally at 24 h, all at 37°C (32).…”