3F72

Crystal Structure of the Staphylococcus aureus pI258 CadC Metal Binding Site 2 Mutant

Summary for 3F72

• Entry DOI: 10.2210/pdb3f72/pdb
• Related: 1U2W
• Descriptor: Cadmium efflux system accessory protein, SODIUM ION (3 entities in total)
• Functional Keywords: cadmium repressor protein, zinc binding site, dimerization site 2 mutant, cadmium resistance, dna-binding, plasmid, transcription, transcription regulation, dna binding protein, metal binding protein, gene regulation
• Biological source: Staphylococcus aureus
• Total number of polymer chains: 6
• Total formula weight: 81888.07

Authors

Kandegedara, A.,Thiyagarajan, S.,Kondapalli, K.C.,Stemmler, T.L.,Rosen, B.P. (deposition date: 2008-11-07, release date: 2009-04-07, Last modification date: 2023-12-27)

Primary citation

Kandegedara, A.,Thiyagarajan, S.,Kondapalli, K.C.,Stemmler, T.L.,Rosen, B.P.
Role of bound Zn(II) in the CadC Cd(II)/Pb(II)/Zn(II)-responsive repressor.
J.Biol.Chem., 284:14958-14965, 2009

PubMed Abstract: The Staphylococcus aureus plasmid pI258 cadCA operon encodes a P-type ATPase, CadA, that confers resistance to Cd(II)/Pb(II)/Zn(II). Expression is regulated by CadC, a homodimeric repressor that dissociates from the cad operator/promoter upon binding of Cd(II), Pb(II), or Zn(II). CadC is a member of the ArsR/SmtB family of metalloregulatory proteins. The crystal structure of CadC shows two types of metal binding sites, termed Site 1 and Site 2, and the homodimer has two of each. Site 1 is the physiological inducer binding site. The two Site 2 metal binding sites are formed at the dimerization interface. Site 2 is not regulatory in CadC but is regulatory in the homologue SmtB. Here the role of each site was investigated by mutagenesis. Both sites bind either Cd(II) or Zn(II). However, Site 1 has higher affinity for Cd(II) over Zn(II), and Site 2 prefers Zn(II) over Cd(II). Site 2 is not required for either derepression or dimerization. The crystal structure of the wild type with bound Zn(II) and of a mutant lacking Site 2 was compared with the SmtB structure with and without bound Zn(II). We propose that an arginine residue allows for Zn(II) regulation in SmtB and, conversely, a glycine results in a lack of regulation by Zn(II) in CadC. We propose that a glycine residue was ancestral whether the repressor binds Zn(II) at a Site 2 like CadC or has no Site 2 like the paralogous ArsR and implies that acquisition of regulatory ability in SmtB was a more recent evolutionary event.

PubMed: 19286656
DOI: 10.1074/jbc.M809179200

Experimental method

X-RAY DIFFRACTION (2.31 Å)