1994/07/01 by David S. Burz, Dorothy Beckett, Nicholas R. Benson +1 · 2 citations
Environmental Science · Biochemistry, Genetics and Molecular Biology · #Bacteriophages and microbial interactions #Bacterial Genetics and Biotechnology #Protein Structure and Dynamics
paper · doi:10.1021/bi00194a003
openalex publication_date 1994/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Dimerization of lambda cI repressor monomers is required for high-affinity binding to bacteriophage lambda operator DNA and is known to involve protein-protein contacts between C-terminal domains of the repressor monomers. In order to address the importance of the C-terminal domain in mediating the oligomeric properties of dimerization and cooperative binding to operator DNA, eight single-site mutant repressors were screened for possible deficiencies in cooperative interactions; all but one of the amino acid substitutions are located within the C-terminal domain. As a prelude to binding studies and the complete characterization of cooperativity mutants of lambda cI repressor (Burz, D. S., & Ackers, G. K. (1994) Biochemistry 33, 8406-8416), the thermodynamics of self-assembly of seven of these mutants was examined from 10(-11) to 10(-5) M total repressor using analytical gel chromatography. Results show that the structural perturbation accompanying single amino acid replacement does not significantly affect the monomer-dimer equilibrium with the exception of that accompanying replacements of serine 228; mutations at that site weaken, by 2-4 kcal/mol, the protein-protein interactions responsible for self-association. An additional mutant repressor, Pro158-->Thr, was also examined and found to associate reversibly from monomers to a species with stoichiometry greater than 2. All mutations increase the apparent Stokes radius of the monomeric form by 2-4.5 A and that of dimers by 1 or 3 A.