1rzm
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Crystal structure of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) from Thermotoga maritima complexed with Cd2+, PEP and E4P
OverviewOverview
3-Deoxy-d-arabino-heptulosonate-7-phosphate synthase (DAHPS) catalyzes the, first reaction of the aromatic biosynthetic pathway in bacteria, fungi, and plants, the condensation of phosphoenolpyruvate (PEP) and, d-erythrose-4-phosphate (E4P) with the formation of DAHP. Crystals of, DAHPS from Thermotoga maritima (DAHPS(Tm)) were grown in the presence of, PEP and metal cofactor, Cd(2+), and then soaked with E4P at 4 degrees C, where the catalytic activity of the enzyme is negligible. The crystal, structure of the "frozen" reaction complex was determined at 2.2A, resolution. The subunit of the DAHPS(Tm) homotetramer consists of an, N-terminal ferredoxin-like (FL) domain and a (beta/alpha)(8)-barrel, domain. The active site located at the C-end of the barrel contains, Cd(2+), PEP, and E4P, the latter bound in a non-productive conformation., The productive conformation of E4P is suggested and a catalytic mechanism, of DAHPS is proposed. The active site of DAHPS(Tm) is nearly identical to, the active sites of the other two known DAHPS structures from Escherichia, coli (DAHPS(Ec)) and Saccharomyces cerevisiae (DAHPS(Sc)). However, the, secondary, tertiary, and quaternary structures of DAHPS(Tm) are more, similar to the functionally related enzyme, 3-deoxy-d-manno-octulosonate-8-phosphate synthase (KDOPS) from E.coli and, Aquiflex aeolicus, than to DAHPS(Ec) and DAHPS(Sc). Although DAHPS(Tm) is, feedback-regulated by tyrosine and phenylalanine, it lacks the extra, barrel segments that are required for feedback inhibition in DAHPS(Ec) and, DAHPS(Sc). A sequence similarity search revealed that DAHPSs of, phylogenetic family Ibeta possess a FL domain like DAHPS(Tm) while those, of family Ialpha have extra barrel segments similar to those of DAHPS(Ec), and DAHPS(Sc). This indicates that the mechanism of feedback regulation in, DAHPS(Tm) and other family Ibeta enzymes is different from that of family, Ialpha enzymes, most likely being mediated by the FL domain.
About this StructureAbout this Structure
1RZM is a Single protein structure of sequence from Thermotoga maritima with CD, PEP and E4P as ligands. Active as 3-deoxy-7-phosphoheptulonate synthase, with EC number 2.5.1.54 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of the reaction complex of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Thermotoga maritima refines the catalytic mechanism and indicates a new mechanism of allosteric regulation., Shumilin IA, Bauerle R, Wu J, Woodard RW, Kretsinger RH, J Mol Biol. 2004 Aug 6;341(2):455-66. PMID:15276836
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