The novel metallo-β-lactamase PNGM-1 from a deep-sea sediment metagenome: crystallization and X-ray crystallographic analysis.

Metallo-β-lactamases (MBLs) are present in major Gram-negative pathogens and environmental species, and pose great health risks because of their ability to hydrolyze the β-lactam rings of antibiotics such as carbapenems. PNGM-1 was the first reported case of a subclass B3 MBL protein that was identified from a metagenomic library from deep-sea sediments that predate the antibiotic era. In this study, PNGM-1 was overexpressed, purified and crystallized. Crystals of native and selenomethionine-substituted PNGM-1 diffracted to 2.10 and 2.30 Å resolution, respectively. Both the native and the selenomethionine-labelled PNGM-1 crystals belonged to the monoclinic space group P21, with unit-cell parameters a = 122, b = 83, c = 163 Å, β = 110°. Matthews coefficient (VM) calculations suggested the presence of 6-10 molecules in the asymmetric unit, corresponding to a solvent content of ∼31-58%. Structure determination is currently in progress.