Crystal Structure of Mox-1, a Unique Plasmid-Mediated Class C β-Lactamase with Hydrolytic Activity towards Moxalactam

Abstract

dMox-1 is a unique plasmid-mediated class C ␤-lactamase that hydrolyzes penicillins, cephalothin, and the expanded-spectrum cephalosporins cefepime and moxalactam. In order to understand the unique substrate profile of this enzyme, we determined the X-ray crystallographic structure of Mox-1 ␤-lactamase at a 1.5-Å resolution. The overall structure of Mox-1 ␤-lactamase resembles that of other AmpC enzymes, with some notable exceptions. First, comparison with other enzymes whose structures have been solved reveals significant differences in the composition of amino acids that make up the hydrogen-bonding network and the position of structural elements in the substrate-binding cavity. Second, the main-chain electron density is not observed in two regions, one containing amino acid residues 214 to 216 positioned in the ⍀ loop and the other in the N terminus of the B3 ␤-strand corresponding to amino acid residues 303 to 306. The last two observations suggest that there is significant structural flexibility of these regions, a property which may impact the recognition and binding of substrates in Mox-1. These important differences allow us to propose that the binding of moxalactam in Mox-1 is facilitated by the avoidance of steric clashes, indicating that a substrate-induced conformational change underlies the basis of the hydrolytic profile of Mox-1 ␤-lactamase.

Atomic‐Resolution Structure of a Class C β‐Lactamase and Its Complex with Avibactam

“…The overall structure of TRU-1 closely resembles that of previously reported class Ce nzymes,s uch as plasmid-encoded MOX-1 (RMSD upon Ca matching 0.78 ), [20] CMY-10 (RMSD 0.87 ), [21] FOX-4 (RMSD 0.69 ), [22] and the chromosomal P. aeruginosa AmpC (RMSD 0.95 ) [19] and E. cloacae P99 AmpC (RMSD 1.14 ). [23] The structure of TRU-1 shows as ulfate anion bound almost at full occupancy (70 %) within the active site ( Figure 3).…”

“… A) Active‐site view of the superimposition of TRU‐1 (gray cartoon) with other class C enzymes (only the R2 loop is shown for clarity in these enzymes). The different amino acids occupying positions 292 and 293 are displayed as sticks in all sequences and colored accordingly: TRU‐1 gray carbon atoms (Ser292, Phe293); FOX‐4 (PDB ID: https://www.rcsb.org/structure/5CGS) cyan carbon atoms (Ser292, Phe293); MOX‐1 (PDB ID: https://www.rcsb.org/structure/3W8K) green carbon atoms (Ile292, Leu293); CMY‐10 (PDB ID: https://www.rcsb.org/structure/1ZKJ) gold carbon atoms (Ile292, Leu293); P. aeruginosa AmpC (PDB ID: https://www.rcsb.org/structure/4GZB) pink carbon atoms (Ala292, Leu293). B) Active‐site view of the superimposition of TRU‐1 (gray cartoon, gray carbon atoms) with FOX‐4 (PDB ID: https://www.rcsb.org/structure/5CGS; R2 loop in cyan cartoon, cyan carbon atoms) and FOX‐4 deacylation‐deficient variant Y150F in complex with cefoxitin (PDB ID: https://www.rcsb.org/structure/5CGX; R2 loop in lilac cartoon, lilac carbon atoms).…”

<p>Synergism of cationic antimicrobial peptide WLBU2 with antibacterial agents against biofilms of multi-drug resistant <em>Acinetobacter baumannii</em> and <em>Klebsiella pneumoniae</em></p>

“…Overall, an increase in WLBU2 MBEC levels was observed compared to planktonic MIC values against K. pneumoniae and A. baumannii . Similarly, two- to fourfold higher MBEC levels of WLBU2 were observed for the treatment of P. aeruginosa abiotic and biotic biofilms compared to the MIC values against planktonic cells 27. Furthermore, it was reported by others that ciprofloxacin, erythromycin, and tobramycin alone were not able to reduce or inhibit biofilm formation by A. baumannii .…”

Molecular Characterization of a Novel Family VIII Esterase with β-Lactamase Activity (PsEstA) from Paenibacillus sp.

“…In addition to conservation of primary sequences, spatial orientation of catalytic residues between class C β-lactamases and family VIII esterases are very similar. As shown in Figure 3, catalytic residues of PsEstA have comparable conformation to those of AmpC [36] and blaMOX-1 [37], as well as EstU1 and Est-Y29. by two domains ( Figure 2B).…”