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Biological NMR Spectroscopy$
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John L. Markley and Stanley J. Opella

Print publication date: 1997

Print ISBN-13: 9780195094688

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780195094688.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 23 October 2021

Flexibility and Function of the Excherichia coli trp Represser

Flexibility and Function of the Excherichia coli trp Represser

(p.29) 5 Flexibility and Function of the Excherichia coli trp Represser
Biological NMR Spectroscopy

M.R. Gryk

O. Jardetzky

Oxford University Press

The trp repressor from Escherichia coli is a DNA binding protein, which in the presence of the ami no acid tryptophan inhibits the transcription of at least five operons: trpEDCBA, trpR, aroH, mtr, and aroL (Zubay et al., 1972; Rose et al., 1973; Zurawski et al., 1981; Heatwole and Somerville, 1991, 1992). The ligand-free form (aporepressor) shows only weak binding (KD ~ 106 - 107 M) to DNA, independent of the nucleotide sequence (Carey, 1988; Hurlburt and Yanofsky, 1990). The tryptophan containing form (holorepressor) binds preferentially to specific operator sequences with a much higher binding constant (KD ~ 1010 - 1011 M) (Carey, 1988; Chou et al., 1989; Hurlburt and Yanofsky, 1990). The binding of the repressoris thus regulated by tryptophan, which acts as a corepressor (Rose et al., 1973). With a molecular weight of approximately 25kD, the trp repressoris one of the smallest regulatory systems known, which makes it attractive as a prototype for the study of the molecular mechanism of allosteric regulation. In the twelve years since it was isolated and purified (Joachimiak et al., 1983), it has become one of the most extensively studied allosteric systems. Although Perutz has justly pointed out that the trp repressoris not allosteric in a classical sense (Perutz, 1989), in fact, the control site is too close to the DNA binding site to separate direct and indirect (allosteric) effects, the system does manifest an essential feature of all allosteric control mechanisms - a structural change induced by ligand binding. Structures of both the apo- and the holorepressor have been determined both by x-ray diffraction (Zhang et al., 1987; Schevitz et al., 1985; Lawson et al., 1988) and by NMR (Arrowsmith et al., 1991a; Zhao et al., 1993). Structures of the operator DNA have also been reported (Lefèvre et al., 1987; Shakked et al., 1994a,b), and several structures of operator-repressor complexes are available: two crystal structures (Otwinowski et al., 1988, Lawson and Carey, 1993), and a family of NMR solution structures (Zhang et al., 1994).

Keywords:   allosteric protein, dynamics, mutant, operator DNA, superrepressor, trp repressor, water

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