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Publication Abstract from PubMed

Lipopolysaccharide (LPS) biosynthesis represents an underexploited target pathway for novel antimicrobial development to combat the emergence of multidrug-resistant bacteria. A key player in LPS synthesis is the enzyme D-arabinose-5-phosphate isomerase (API), which catalyzes the reversible isomerization of D-ribulose-5-phosphate to D-arabinose-5-phosphate, a precursor of 3-deoxy-D-manno-octulosonate that is an essential residue of the LPS inner core. API is composed of two main domains: an N-terminal sugar isomerase domain (SIS) and a pair of cystathionine-beta-synthase domains of unknown function. As the three-dimensional structure of an enzyme is a prerequisite for the rational development of novel inhibitors, we present here the crystal structure of the SIS domain of a catalytic mutant (K59A) of E. coli D-arabinose-5-phosphate isomerase at 2.6-A resolution. Our structural analyses and comparisons made with other SIS domains highlight several potentially important active site residues. In particular, the crystal structure allowed us to identify a previously unpredicted His residue (H88) located at the mouth of the active site cavity as a possible catalytic residue. On the basis of such structural data, subsequently supported by biochemical and mutational experiments, we confirm the catalytic role of H88, which appears to be a generally conserved residue among two-domain isomerases.

Probing the active site of the sugar isomerase domain from E. coli arabinose-5-phosphate isomerase via X-ray crystallography.,Gourlay LJ, Sommaruga S, Nardini M, Sperandeo P, Deho G, Polissi A, Bolognesi M Protein Sci. 2010 Dec;19(12):2430-9. doi: 10.1002/pro.525. PMID:20954237^[4]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.