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Purification and characterization of repressor of temperate S. aureus phage phi11.

Authors :
Das M
Ganguly T
Chattoraj P
Chanda PK
Bandhu A
Lee CY
Sau S
Source :
Journal of biochemistry and molecular biology [J Biochem Mol Biol] 2007 Sep 30; Vol. 40 (5), pp. 740-8.
Publication Year :
2007

Abstract

To gain insight into the structure and function of repressor proteins of bacteriophages of gram-positive bacteria, repressor of temperate Staphylococcus aureus phage phi11 was undertaken as a model system here and purified as an N-terminal histidine-tagged variant (His-CI) by affinity chromatography. A approximately 19 kDa protein copurified with intact His-CI (approximately 30 kDa) at low level was resulted most possibly due to partial cleavage at its Ala-Gly site. At approximately 10 nM and higher concentrations, His-CI forms significant amount of dimers in solution. There are two repressor binding sites in phi11 cI-cro intergenic region and binding to two sites occurs possibly by a cooperative manner. Two sites dissected by HincII digestion were designated operators O(L) and O(R), respectively. Equilibrium binding studies indicate that His-CI binds to O(R) with a little more strongly than O(L) and binding species is probably dimeric in nature. Interestingly His-CI binding affinity reduces drastically at elevated temperatures (32-42 degrees C). Both O(L) and O(R) harbor a nearly identical inverted repeat and studies show that phi11 repressor binds to each repeat efficiently. Additional analyses indicate that phi11 repressor, like lambda repressor, harbors an N-terminal domain and a C-terminal domain which are separated by a hinge region. Secondary structure of phi11 CI even nearly resembles to that of lambda, phage repressor though they differ at sequence level. The putative N-terminal HTH (helix-turn-helix) motif of phi11 repressor belongs to the HTH -XRE-family of proteins and shows significant identity to the HTH motifs of some proteins of evolutionary distant organisms but not to HTH motifs of most S. aureus phage repressors.

Details

Language :
English
ISSN :
1225-8687
Volume :
40
Issue :
5
Database :
MEDLINE
Journal :
Journal of biochemistry and molecular biology
Publication Type :
Academic Journal
Accession number :
17927908
Full Text :
https://doi.org/10.5483/bmbrep.2007.40.5.740