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Structure of a Dimeric Lac Repressor with C-terminal Deletion and K84L SubstitutionStructure of a Dimeric Lac Repressor with C-terminal Deletion and K84L Substitution
Structural highlights
Function[LACI_ECOLI] Repressor of the lactose operon. Binds allolactose as an inducer. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedA single amino acid substitution, K84L, in the Escherichia coli lac repressor produces a protein that has substantially increased stability compared to wild-type. However, despite the increased stability, this altered tetrameric repressor has a tenfold reduced affinity for operator and greatly decreased rate-constants of inducer binding as well as a reduced phenotypic response to inducer in vivo. To understand the dramatic increase in stability and altered functional properties, we have determined the X-ray crystal structures of a dimeric repressor with and without the K84L substitution at resolutions of 1.7 and 3.0 A, respectively. In the wild-type dimer, K84-11, Lys84 forms electrostatic interactions at the monomer-monomer interface and is partially exposed to solvent. In the K84L-11 substituted protein there is reorientation of the N-subdomains, which allows the leucine to become deeply buried at the monomer-monomer interface. This reorientation of the N-subdomains, in turn, results in an alteration of hydrogen bonding, ion pairing, and van der Waals interactions at the monomer-monomer interface. The lysine residue at position 84 appears to exert its key effects by destabilizing the "optimal" conformation of the repressor, effectively loosening the dimer interface and allowing the repressor to adopt the conformations necessary to function as a molecular switch. Structure of a variant of lac repressor with increased thermostability and decreased affinity for operator.,Bell CE, Barry J, Matthews KS, Lewis M J Mol Biol. 2001 Oct 12;313(1):99-109. PMID:11601849[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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