Subdividing repressor function: DNA binding affinity, selectivity, and allostery can be altered by amino acid substitution of nonconserved residues in a LacI/GalR homologue.

ABSTRACT: Many mutations that impact protein function occur at residues that do not directly contact ligand. To understand the functional contributions from the sequence that links the DNA-binding and regulatory domains of the LacI/GalR homologues, we have created a chimeric protein (LLhP), which comprises the LacI DNA-binding domain, the LacI linker, and the PurR regulatory domain. Although DNA binding site residues are identical in LLhP and LacI, thermodynamic measurements of DNA binding affinity show that LLhP does not discriminate between alternative DNA ligands as well as LacI. In addition, small-angle scattering experiments show that LLhP is more compact than LacI. When DNA is released, LacI shows a 20 A increase in length that was previously attributed to unfolding of the linker. This change

SUBMITTER: Zhan H 

PROVIDER: S-EPMC2561905 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature