2QJS

Stenotrophomonas maltophilia L1 metallo-beta-lactamase Asp-120 Asn mutant

Summary for 2QJS

• Entry DOI: 10.2210/pdb2qjs/pdb
• Related: 1SML 2AIO 2QIN
• Descriptor: Metallo-beta-lactamase L1, ZINC ION (3 entities in total)
• Functional Keywords: metallo-beta-lactamase, hydrolase, dinculear, binculear
• Biological source: Stenotrophomonas maltophilia
• Cellular location: Periplasm : P52700
• Total number of polymer chains: 4
• Total formula weight: 115481.15

Authors

Crisp, J.,Conners, R.,Spencer, J. (deposition date: 2007-07-09, release date: 2007-08-21, Last modification date: 2024-11-13)

Primary citation

Crisp, J.,Conners, R.,Garrity, J.D.,Carenbauer, A.L.,Crowder, M.W.,Spencer, J.
Structural Basis for the Role of Asp-120 in Metallo-beta-lactamases
Biochemistry, 46:10664-10674, 2007

PubMed Abstract: Metallo-beta-lactamases (mbetals) are zinc-dependent enzymes that hydrolyze a wide range of beta-lactam antibiotics. The mbetal active site features an invariant Asp-120 that ligates one of the two metal ions (Zn2) and a metal-bridging water/hydroxide (Wat1). Previous studies show that substitutions at Asp-120 dramatically affect mbetal activity, but no consensus exists as to its role in beta-lactam turnover. Here we present crystal structures of the Asn and Cys mutants of Asp-120 of the L1 mbetal from Stenotrophomonas maltophilia. Both mutants retain a dinuclear zinc center with Wat1 present. In the essentially inactive Cys enzyme Zn2 is displaced to a more buried position relative to that in the wild-type enzyme. In the catalytically impaired Asn enzyme the coordination of Zn2 is altered, neither it nor Wat1 is coordinated by Asn-120, and the N-terminal 19 amino acids, important to cooperative interactions between subunits in the wild-type enzyme, are disordered. Comparison with the structure of L1 complexed with the hydrolyzed oxacephem moxalactam suggests that in the Cys mutant Zn2 can no longer make stabilizing interactions with anionic nitrogen species formed in the hydrolytic reaction. The diminished activity of the Asn mutant arises from a combination of loss of intersubunit interactions and impaired proton transfer to, and reduced interaction of Zn2 with, the substrate amide nitrogen. We conclude that, while interactions of Asp-120 with active site water molecules are important to proton transfer and possibly nucleophilic attack by Wat1, its primary role is to optimally position Zn2 for catalytically important interactions with the charged amide nitrogen of substrate.

PubMed: 17715946
DOI: 10.1021/bi700707u

Experimental method

X-RAY DIFFRACTION (2.25 Å)