Protein-protein interactions regulate and drive biological processes and
understanding the assembly of these interactions is important. The LysR-Type
Transcriptional Regulators (LTTRs) are a large family of transcriptional regulators
found in prokaryotes. I have used the LTTRs as a model for protein specificity. In order
to understand a residue's contribution to oligomerization, alanine-scanning mutagenesis
was used to probe the contribution of residues identified from in silico analysis of two
proteins: OxyR and CynR. The contribution of the residues to oligomerization was
characterized using lcI repressor fusions. In OxyR, seven residues were identified as
hot spots. Moreover, these hot spots are not especially conserved. The interaction surface
of OxyR was mapped onto a multiple sequence alignment of the LTTR family. This
mapping identified putative contacts in the CynR regulatory domain dimer interface.
Combined with the in vivo testing, three residues were identified as hot spots. The
residues identified in OxyR and CynR do not overlap. To investigate the assembly of the
LTTRs I used a negative-dominance assay with lcI repressor fusions. Taken together, I
show that the LTTRs in E. coli K-12 are mostly specific in their interactions.
- Hu, James Professor