3qq1

Publication Abstract from PubMed

3-Deoxy-D-<i>manno</i>-octulosonate 8-phosphate synthase (KDO8PS) catalyzes the reaction between three-carbon phosphoenolpyruvate (PEP) and five-carbon D-arabinose 5-phosphate (A5P), generating KDO8P, a key intermediate in the biosynthetic pathway to 3-deoxy-D-<i>manno</i>-octulosonate, a component of the lipopolysaccharide of the Gram-negative bacterial cell wall. Both metal-dependent and metal-independent forms of KDO8PS have been characterized. KDO8PS is evolutionarily and mechanistically related to the first enzyme of the shikimate pathway, the obligately divalent metal-ion-dependent 3-deoxy-D-<i>arabino</i>-heptulosonate 7-phosphate synthase (DAH7PS) that couples PEP and four-carbon D-erythrose 4-phosphate (E4P) to give DAH7P. In KDO8PS an absolutely conserved KANRS motif forms part of the A5P binding site, whereas in DAH7PS an absolutely conserved KPR(S/T) motif accommodates E4P. Here, we have characterized four mutants of this motif (AANRS, KAARS, KARS and KPRS) in metal-dependent KDO8PS from <i>Acidithiobacillus ferrooxidans</i> and metal-independent KDO8PS from <i>Neisseria meningitidis</i> in order to test the roles of the universal Lys and the AlaAsn portion of the KANRS motif. The X-ray structures, determined for the <i>N. meningitidis</i> KDO8PS mutants, indicated no gross structural penalty resulting from mutation, but the subtle changes observed in the active sites of these mutant proteins correlated with their altered catalytic function: 1) the AANRS mutations destroyed catalytic activity; 2) the KAARS mutations lowered substrate selectivity, as well as activity; 3) replacing KANRS by KARS or KPRS destroyed KDO8PS activity, but did not produce a functional DAH7PS. Thus, Lys is critical to catalysis and other changes are necessary to switch substrate specificity for both the metal-independent and metal-dependent forms of these enzymes.<i></i>

Targeting the role of a key conserved motif for substrate selection and catalysis by 3-deoxy-D-<i>manno</i>-octulosonate 8-phosphate synthase.,Allison TM, Hutton RD, Cochrane FC, Yeoman JA, Jameson GB, Parker EJ Biochemistry. 2011 Mar 25. PMID:21438567^[1]

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