Protein Science, Vol 7, Issue 2 512-515, Copyright © 1998 by Cold Spring Harbor Laboratory Press

FOR THE RECORD

A LexA mutant repressor with a relaxed inter-domain linker

P. OERTEL-BUCHHEIT, J. REINBOLT, M. JOHN, M. GRANGER-SCHNARR and M. SCHNARR
Institut de Biologie Moleculaire et Cellulaire, UPR 9002 du CNRS, 15, rue Rene Descartes, F-67084 Strasbourg Cedex, France

The LexA protein is part of a large family of prokaryotic transcriptional repressors that contain an amino-terminal DNA binding domain and a carboxy-terminal dimerization domain. These domains are separated by a linker or hinge region, which is generally considered to be rather flexible and unconstrained. So far, no structure of any of the full-length repressors is available. Here we show that a mutant LexA repressor harboring several point mutations in the hinge region gets sensitive to trypsin and Glu-C cleavage over a segment of at least 20 amino acids, whereas the LexA wild-type hinge region is resistant to these proteases. These data are not compatible with the hypothesis of an fully flexible and/or unstructured inter-domain linker and suggest that the LexA hinge region is, in fact, constrained by contacts with the carboxy-terminal domain and/or a fairly stable local structure of the linker region.
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