Motion in Trp Repressor (TrpR) [trpr]

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Classification Known Domain Motion, Shear Mechanism [D-s-2]

Structures 1WRP Conformation 1 [ PartsList ] 2WRP Conformation 2 [ PartsList ] 3WRP Conformation 3 [ PartsList ]

Description Shear motion between 2 helices adjusts position of helix-turn-helix reading head domain to enable it to bind DNA. The trp repressor is a small protein that regulates three operons involved in the synthesis of tryptophan. It is a dimer, and each subunit contains six helices, divided between two domains. The central core of the molecule is formed from four helices from each subunit. On either side of this core, helix-turn-helix motifs form two symmetrically arranged DNA 'reading head' domains. Between the central core and the reading-head domains, there are two binding sites for L-tryptophan, which need to be filled for trp repressor to recognize DNA. Comparison of the holo and apo forms of the repressor shows that the binding of L-tryptophan shifts alpha carbons in the reading head domain by up to 4 A. These shifts are produced by separate shear motions of the two helices in the reading-head domain (0.75 to1.5 A, 5 to 20 degrees). These helix motions move the reading-head domains further apart than they are in the apo form so they are correctly separated to bind DNA.

Particular values describing motion Creation Date = 19970822 Modification Date = 19970822 Experimental Methods = x (Traditional x-ray)

References C L Lawson, R Zhang, R W Schevitz, Z Otwinowski, A Joachimiak and P B Sigler (1988). Flexibility of the DNA-Binding Domains of the trp Repressor. Proteins. 3: 18-31. [Medline info for 94174274]

Morphs

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Best representative Morph Morph name Structure #1 Structure #2 Residues [ ] [ ]

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Copyright 1995-2005 M. Gerstein, W. Krebs, S. Flores, N. Echols, and others
Email: Mark.Gerstein _at_ yale.edu