IMP-type metallo-β-lactamases (MBLs) are exogenous zinc metalloenzymes that hydrolyze a broad range of β-lactams, including carbapenems. Here we report the crystal structure of IMP-18, an MBL cloned from Pseudomonas aeruginosa, at 2.0-Å resolution. The overall structure of IMP-18 resembles that of IMP-1, with an αβ/βα "folded sandwich" configuration, but the loop that covers the active site has a distinct conformation. The relationship between IMP-18's loop conformation and its kinetic properties was investigated by replacing the amino acid residues that can affect the loop conformation (Lys44, Thr50, and Ile69) in IMP-18 with those occupying the corresponding positions in the well-described enzyme IMP-1. The replacement of Thr50 with Pro considerably modified IMP-18's kinetic properties, specifically those pertaining to meropenem, with the kcat/Km value increased by an order of magnitude. The results indicate that this is a key residue that defines the kinetic properties of IMP-type β-lactamases.
ID: DKhYXcV74
Submitter: Paulie Dang
Submission Date: March 28, 2020, 5:45 p.m.
Version: 1
Explanation of amino acid numbering: Residues K26N, T32P, and I51F that were mutated in this study are called residues K44N, T50P, and I69F respectively in the paper.
Number of data points | 240 |
Proteins | IMP-18 Crystal Structure |
Unique complexes | 40 |
Assays/Quantities/Protocols | Experimental Assay: kcat/Km ; Experimental Assay: Km ; Experimental Assay: kcat ; Derived Quantity: SD of kcat/Km ; Derived Quantity: SD of Km ; Derived Quantity: SD of kcat |
Libraries | Kinetic Assay Data |
Colors: | D | E | R | H | K | S | T | N | Q | A | V | I | L | M | F | Y | W | C | G | P |
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