HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 277, Issue 15, 13155-13166, April 12, 2002

This Article Full Text Full Text (PDF) All Versions of this Article: 277/15/13155    most recent M111877200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dobritzsch, D. Articles by Lindqvist, Y. Search for Related Content PubMed PubMed Citation Articles by Dobritzsch, D. Articles by Lindqvist, Y. Social Bookmarking                      What's this?

Crystal Structure of the Productive Ternary Complex of Dihydropyrimidine Dehydrogenase with NADPH and 5-Iodouracil
IMPLICATIONS FOR MECHANISM OF INHIBITION AND ELECTRON TRANSFER^*

Doreen Dobritzsch^§, Stefano Ricagno^¶, Gunter Schneider, Klaus D. Schnackerz, and Ylva Lindqvist^**

From the  Division of Molecular Structural Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden and  Theodor-Boveri-Institut für Biowissenschaften, Physiologische Chemie I, Am Hubland, D-97074 Würzburg, Germany

Dihydroprymidine dehydrogenase catalyzes the first and rate-limiting step in pyrimidine degradation by converting pyrimidines to the corresponding 5,6- dihydro compounds. The three-dimensional structures of a binary complex with the inhibitor 5-iodouracil and two ternary complexes with NADPH and the inhibitors 5-iodouracil and uracil-4-acetic acid were determined by x-ray crystallography. In the ternary complexes, NADPH is bound in a catalytically competent fashion, with the nicotinamide ring in a position suitable for hydride transfer to FAD. The structures provide a complete picture of the electron transfer chain from NADPH to the substrate, 5-iodouracil, spanning a distance of 56 Å and involving FAD, four [Fe-S] clusters, and FMN as cofactors. The crystallographic analysis further reveals that pyrimidine binding triggers a conformational change of a flexible active-site loop in the /-barrel domain, resulting in placement of a catalytically crucial cysteine close to the bound substrate. Loop closure requires physiological pH, which is also necessary for correct binding of NADPH. Binding of the voluminous competitive inhibitor uracil-4-acetic acid prevents loop closure due to steric hindrance. The three-dimensional structure of the ternary complex enzyme-NADPH-5-iodouracil supports the proposal that this compound acts as a mechanism-based inhibitor, covalently modifying the active-site residue Cys-671, resulting in S-(hexahydro-2,4-dioxo-5-pyrimidinyl)cysteine.

The atomic coordinates and the structure factors (code 1gte (DPD|b15IU), 1gth (DPD|b15IU|b1NADPH), and 1gt8 (DPD|b1UAA|b1NADPH)) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				A. Osterman A hidden metabolic pathway exposed PNAS, April 11, 2006; 103(15): 5637 - 5638. [Full Text] [PDF]