Structural Basis for the Selective Pb(II) Recognition of Metalloregulatory Protein PbrR691

The transcription regulator PbrR691, one of the MerR family proteins, shows extremely high sensitivity and selectivity toward Pb(II) in Ralstonia metallidurans CH34. Here, we present the crystal structure of PbrR691 in complex with Pb(II) at 2.0 angstrom resolution. The Pb(II) coordinates with three conserved cysteines and adopts a unique trigonal-pyramidal (hemidirected) geometry. To our knowledge, the PbrR691-Pb(II) structure provides the first three-dimensional visualization of a functional hemidirected lead(II) thiolate coordinate geometry in a protein.