1d1l
CRYSTAL STRUCTURE OF CRO-F58W MUTANT
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OverviewOverview
It was previously shown that the Cro repressor from phage lambda, which is, a dimer, can be converted into a stable monomer by a five-amino acid, insertion. Phe58 is the key residue involved in this transition, switching, from interactions which stabilize the dimer to those which stabilize the, monomer. Structural studies, however, suggested that Phe58 did not, penetrate into the core of the monomer as well as it did into the native, dimer. This was strongly supported by the finding that certain, core-repacking mutations, including in particular, Phe58-->Trp, increased, the stability of the monomer. Unexpectedly, the same substitution also, increased the stability of the native dimer. At the same time it decreased, the affinity of the dimer for operator DNA. Here we describe the crystal, structures of the Cro F58W mutant, both as the monomer and as the dimer., The F58W monomer crystallized in a form different from that of the, original monomer. In contrast to that structure, which resembled the, DNA-bound form of Cro, the F58W monomer is closer in structure to, wild-type (i.e. non-bound) Cro. The F58W dimer also crystallizes in a form, different from the native dimer but has a remarkably similar overall, structure which tends to confirm the large changes in conformation of Cro, on binding DNA. Introduction of Trp58 perturbs the position occupied by, the side-chain of Arg38, a DNA-contact residue, providing a structural, explanation for the reduction in DNA-binding affinity.The improved thermal, stability is seen to be due to the enhanced solvent transfer free energy, of Trp58 relative to Phe58, supplemented in the dimer structure, although, not the monomer, by a reduction in volume of internal cavities.
About this StructureAbout this Structure
1D1L is a Single protein structure of sequence from Enterobacteria phage lambda with SO4 as ligand. Full crystallographic information is available from OCA.
ReferenceReference
The structural basis for enhanced stability and reduced DNA binding seen in engineered second-generation Cro monomers and dimers., Rupert PB, Mollah AK, Mossing MC, Matthews BW, J Mol Biol. 2000 Mar 3;296(4):1079-90. PMID:10686105
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