Abstract
Metallo-β-lactamase (MBL) superfamily proteins have a common αβ/βα sandwich fold and perform a variety of functions through metal-mediated catalysis. However, because of the enormous scale of this superfamily, only a small percentage of the proteins belonging to the superfamily have been annotated structurally or functionally to date. Therefore, much remains unknown about the MBL superfamily proteins. Here, TW9814, a hypothetical MBL superfamily protein, was structurally and functionally investigated. Guided by the crystal structure of dimeric TW9814, it was demonstrated that TW9814 functions as a phosphodiesterase (PDE) in the presence of divalent metal ions such as manganese(II) or nickel(II). A docking model between TW9814 and the substrate bis(p-nitrophenyl)phosphate (bpNPP) showed the importance of the dimerization of TW9814 for its bpNPP-hydrolyzing activity and for the interaction between the enzyme and the substrate. TW9814 showed outstanding catalytic efficiency (k
cat/K
m) under alkaline conditions compared with other PDEs. The activity of TW9814 appears to be regulated through a disulfide bond, which is a feature that is not present in other MBL superfamily members. This study provides a platform for the functional characterization of other hypothetical proteins of the MBL or other superfamilies.
Funder
National Research Foundation of Korea
Ministry of Oceans and Fisheries
Publisher
International Union of Crystallography (IUCr)