SloR from is a member of the DtxR family of metal ion-dependent regulatory proteins that, similar to orthologs from other streptococcal species, mediates the expression of a number of virulence genes in a manganese-dependent fashion. Recent work in our laboratories has focused on the capacity of SloR dimers to bind three adjacent sites covering 72 base pairs in the promoter region upstream of the sloABC operon, which encodes a manganese transporter. We have discovered cooperative binding between dimers in solution assays, and have obtained low resolution images of the three-dimer complex with DNA by electron microscopy (EM) using negative staining. Our attempts to extend the EM studies to cryo-conditions have been complicated by sample aggregation. We have investigated the structural origins of cooperativity and aggregation through site-directed mutagenesis, guided by structure and sequence analysis. The mutation of surface residue Phe187 to alanine reduces aggregation, and on-going studies are exploring the effect of that mutation and others on cooperativity.

Structural and solution studies of DNA-binding by SloR, A Mn-dependent regulatory protein from Streptococcus mutans

255th National Meeting (2018)

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