Regulation of the Expression of the β‑Lactam Antibiotic-Resistance Determinants in Methicillin-Resistant <i>Staphylococcus aureus</i> (MRSA)

β-Lactam antibiotics have faced obsolescence with the emergence of methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). A complex set of events ensues upon exposure of MRSA to these antibiotics, which culminates in proteolysis of BlaI or MecI, two gene repressors, and results in the induction of resistance. We report studies on the mechanism of binding of these gene repressors to the operator regions by fluorescence anisotropy. Within the range of <i>in vivo</i> concentrations for BlaI and MecI, these proteins interact with their regulatory elements in a reversible manner, as both a monomer and a dimer

Reactions of All <i>Escherichia coli</i> Lytic Transglycosylases with Bacterial Cell Wall

The reactions of all seven <i>Escherichia coli</i> lytic transglycosylases with purified bacterial sacculus are characterized in a quantitative manner. These reactions, which initiate recycling of the bacterial cell wall, exhibit significant redundancy in the activities of these enzymes along with some complementarity. These discoveries underscore the importance of the functions of these enzymes for recycling of the cell wall

Inhibitors for Bacterial Cell-Wall Recycling

Gram-negative bacteria have evolved an elaborate process for the recycling of their cell wall, which is initiated in the periplasmic space by the action of lytic transglycosylases. The product of this reaction, β-d-<i>N-</i>acetylglucosamine-(1→4)-1,6-anhydro-β-d-<i>N-</i>acetylmuramyl-l-Ala-γ-d-Glu-<i>meso</i>-DAP-d-Ala-d-Ala (compound <b>1</b>), is internalized to begin the recycling events within the cytoplasm. The first step in the cytoplasmic recycling is catalyzed by the NagZ glycosylase, which cleaves in a hydrolytic reaction the <i>N</i>-acetylglucosamine glycosidic bond of metabolite <b>1</b>. The reactions catalyzed by both the lytic glycosylases and NagZ are believed to involve oxocarbenium transition species. We describe herein the synthesis and evaluation of four iminosaccharides as possible mimetics of the oxocarbenium species, and we disclose one as a potent (compound <b>3</b>, <i>K</i>_i = 300 ± 15 nM) competitive inhibitor of NagZ