Structural Determinants of Substrate Recognition in the HAD Superfamily Member D-Glycero-D-manno-Heptose 1,7-bisphosphate Phosphatase, GmhB

The haloalkanoic acid dehalogenase (HAD) enzyme superfamily is the largest family of phosphohydrolases. In HAD members, the structural elements that provide the binding interactions that support substrate specificity are separated from those that orchestrate catalysis. For most HAD phosphatases, a cap domain functions in substrate recognition. However, for the HAD phosphatases that lack a cap domain, an alternate strategy for substrate selection must be operative. One such HAD phosphatase, GmhB of the HisB subfamily, was selected for structure−function analysis. Herein, the X-ray crystallographic structures of Escherichia coli GmhB in the apo form (1.6 A resolution), in a complex with Mg2+ and orthophosphate (1.8 A resolution), and in a complex with Mg2+ and d-glycero-d-manno-heptose 1β,7-bisphosphate (2.2 A resolution) were determined, in addition to the structure of Bordetella bronchiseptica GmhB bound to Mg2+ and orthophosphate (1.7 A resolution). The structures show that in place of a cap domain, the ...