Linked Life Data

16464095

Source:http://linkedlifedata.com/resource/pubmed/id/16464095

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
2006-2-8
pubmed:abstractText
The Zn(II)/Co(II)-sensing transcriptional repressor, Staphylococcus aureus CzrA, is a homodimer containing a symmetry-related pair of subunit-bridging tetrahedral N(3)O metal sensor coordination sites. A metal-induced quaternary structural change within the homodimer is thought to govern the biological activity of this and other metal sensor proteins. Here, we exploit covalent (Gly(4)Ser)(n)() linkers of variable length in "fused" CzrAs, where n = 1 (designated 5L-fCzrA), 2 (10L-fCzrA), or 3 (15L-fCzrA), as molecular rulers designed to restrict any quaternary structural changes that are associated with metal binding and metal-mediated allosteric regulation of DNA binding to varying degrees. While 15L-fCzrA exhibits properties most like homodimeric CzrA, shortening the linker in 10L-fCzrA abolishes negative homotropic cooperativity of Zn(II) binding and reduces DNA binding affinity of the apoprotein significantly. Decreasing the linker length further in 5L-fCzrA effectively destroys one metal site altogether and further reduces DNA binding affinity. However, Zn(II) negatively regulates DNA binding of all fCzrAs, with allosteric coupling free energies (DeltaG(1)(c)) of 4.6, 3.1, and 2.7 kcal mol(-1) for 15L-, 10L-, and 5L-fCzrAs, respectively. Introduction of a single nonliganding H97N substitution into either the N-terminal or C-terminal protomer domain in 10L-fCzrA results in DeltaG(1)(c) = 2.6 kcal mol(-1) or approximately 83% that of 10L-fCzrA; in contrast, homodimeric H97N CzrA gives DeltaG(1)(c) = 0. (1)H-(15)N HSQC spectra acquired for wt-, 10L-fCzrA and H97N 10L-fCzrA in various Zn(II) ligation states reveal that the allosteric change of the protomer domains within the fused dimer is independent and not concerted. Thus, occupancy of a single metal site by Zn(II) introduces asymmetry into the CzrA homodimer that leads to significant allosteric regulation of DNA binding.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0002-7863
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
128
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1937-47
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Structural insights into homo- and heterotropic allosteric coupling in the zinc sensor S. aureus CzrA from covalently fused dimers.
pubmed:affiliation
Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural