1drv

From Proteopedia

Revision as of 12:35, 18 December 2007

ESCHERICHIA COLI DHPR/ACNADH COMPLEX

Overview

E. coli dihydrodipicolinate reductase exhibits unusual nucleotide, specificity, with NADH being kinetically twice as effective as NADPH as a, reductant as evidenced by their relative V/K values. To investigate the, nature of the interactions which determine this specificity, we performed, isothermal titration calorimetry to determine the thermodynamic parameters, of binding and determined the three-dimensional structures of the, corresponding enzyme-nucleotide complexes. The thermodynamic binding, parameters for NADPH and NADH were determined to be Kd = 2.12 microM, delta G degree = -7.81 kcal mol-1, delta H degree = -10.98 kcal mol-1, and, delta S degree = -10.5 cal mol-1 deg-1 and Kd = 0.46 microM, delta G, degree = -8.74 kcal mol-1, delta H degree = -8.93 kcal mol-1, and delta S, degree = 0.65 cal mol-1 deg-1, respectively. The structures of DHPR, complexed with these nucleotides have been determined at 2.2 A resolution., The 2'-phosphate of NADPH interacts electrostatically with Arg39, while in, the NADH complex this interaction is replaced by hydrogen bonds between, the 2' and 3' adenosyl ribose hydroxyls and Glu38. Similar studies were, also performed with other pyridine nucleotide substrate analogs to, determine the contributions of individual groups on the nucleotide to the, binding affinity and enthalpic and entropic components of the free energy, of binding, delta G degree. Analogs lacking the 2'-phosphate containing, homologs. For all analogs, the total binding free energy can be shown to, include compensating enthalpic and entropic contributions to the, association constants. The entropy contribution appears to play a more, important role in the binding of the nonphosphorylated analogs than in the, binding of the phosphorylated analogs.

About this Structure

1DRV is a Single protein structure of sequence from Escherichia coli with A3D as ligand. Active as Dihydrodipicolinate reductase, with EC number 1.3.1.26 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Interaction of pyridine nucleotide substrates with Escherichia coli dihydrodipicolinate reductase: thermodynamic and structural analysis of binary complexes., Reddy SG, Scapin G, Blanchard JS, Biochemistry. 1996 Oct 15;35(41):13294-302. PMID:8873595

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