PMID:19617363

Citation	Zhang, Q, Gao, F, Peng, H, Cheng, H, Liu, Y, Tang, J, Thompson, J, Wei, G, Zhang, J, Du, Y, Yan, J and Gao, GF (2009) Crystal structures of Streptococcus suis mannonate dehydratase (ManD) and its complex with substrate: genetic and biochemical evidence for a catalytic mechanism. J. Bacteriol. 191:5832-7
Abstract	Mannonate dehydratase (ManD) is found only in certain bacterial species, where it participates in the dissimilation of glucuronate. ManD catalyzes the dehydration of d-mannonate to yield 2-keto-3-deoxygluconate (2-KDG), the carbon and energy source for growth. Selective inactivation of ManD by drug targeting is of therapeutic interest in the treatment of human Streptococcus suis infections. Here, we report the overexpression, purification, functional characterization, and crystallographic structure of ManD from S. suis. Importantly, by Fourier transform mass spectrometry, we show that 2-KDG is formed when the chemically synthesized substrate (d-mannonate) is incubated with ManD. Inductively coupled plasma-mass spectrometry revealed the presence of Mn(2+) in the purified protein, and in the solution state catalytically active ManD exists as a homodimer of two 41-kDa subunits. The crystal structures of S. suis ManD in native form and in complex with its substrate and Mn(2+) ion have been solved at a resolution of 2.9 A. The core structure of S. suis ManD is a TIM barrel similar to that of other members of the xylose isomerase-like superfamily. Structural analyses and comparative amino acid sequence alignments provide evidence for the importance of His311 and Tyr325 in ManD activity. The results of site-directed mutagenesis confirmed the functional role(s) of these residues in the dehydration reaction and a plausible mechanism for the ManD-catalyzed reaction is proposed.
Links	PubMed PMC2737975 Online version:10.1128/JB.00599-09
Keywords	Catalysis; Crystallization; Crystallography, X-Ray; Hydro-Lyases/chemistry; Hydro-Lyases/genetics; Hydro-Lyases/metabolism; Kinetics; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Conformation; Streptococcus suis/enzymology; Streptococcus suis/genetics; Sugar Acids/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
STRSU:A0A142UME2		GO:0008927 : mannonate dehydratase activity	ECO:0000315:		F		Based on fig. 1 (mass spec), two dominant peaks were found after incubation with mannonate dehydratase(ManD). The first peak corresponds to remaining substrate(D-mannonate), whereas the second peak is consistent with formation of the expected protonated dehydration product, 2-KDG (IDA inferred) Based on table 2, wild type ManD show high affinity to the substrate but the mutant protein Y325F was catalytically inactive while the activity of H311A was only 2.4% that of the native enzyme. The results of site-directed mutagenesis confirmed the functional of these residues in the dehydration reaction (IMP inferred)	complete CACAO 4480
STRSU:A0A142UME2	enables	GO:0008927: mannonate dehydratase activity	ECO:0000315: mutant phenotype evidence used in manual assertion		F		Seeded From UniProt	complete

References

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