1ymq
HAD Superfamily Phosphotransferase Substrate Diversification: Structure and Function Analysis of the HAD Subclass IIB Sugar Phosphatase BT4131
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OverviewOverview
The BT4131 gene from the bacterium Bacteroides thetaiotaomicron VPI-5482, has been cloned and overexpressed in Escherichia coli. The protein, a, member of the haloalkanoate dehalogenase superfamily (subfamily IIB), was, purified to homogeneity, and its X-ray crystal structure was determined, to1.9 A resolution using the molecular replacement phasing method. BT4131, was shown by an extensive substrate screen to be a broad-range sugar, phosphate phosphatase. On the basis of substrate specificity and gene, context, the physiological function of BT4131 in chitin metabolism has, been tentatively assigned. Comparison of the BT4131 structure alpha/beta, cap domain structure with those of other type IIB enzymes, (phosphoglycolate phosphatase, trehalose-6-phosphate phosphatase, and, proteins of unknown function known as PDB entries , , and ) identified two, conserved loops (BT4131 residues 172-182 and 118-130) in the, alphabetabeta(alphabetaalphabeta)alphabetabeta type caps and one conserved, loop in the alphabetabetaalphabetabeta type caps, which contribute, residues for contact with the substrate leaving group. In BT4131, the two, loops contribute one polar and two nonpolar residues to encase the, displaced sugar. This finding is consistent with the lax specificity, BT4131 has for the ring size and stereochemistry of the sugar phosphate., In contrast, substrate docking showed that the high-specificity, phosphoglycolate phosphatase (PDB entry ) uses a single substrate, specificity loop to position three polar residues for interaction with the, glycolate leaving group. We show how active site "solvent cages" derived, from analysis of the structures of the type IIB HAD phosphatases could be, used in conjunction with the identity of the residues stationed along the, cap domain substrate specificity loops, as a means of substrate, identification.
About this StructureAbout this Structure
1YMQ is a Single protein structure of sequence from Bacteroides thetaiotaomicron with MG and SO4 as ligands. Full crystallographic information is available from OCA.
ReferenceReference
HAD superfamily phosphotransferase substrate diversification: structure and function analysis of HAD subclass IIB sugar phosphatase BT4131., Lu Z, Dunaway-Mariano D, Allen KN, Biochemistry. 2005 Jun 21;44(24):8684-96. PMID:15952775
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