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Identification of the domains for DNA binding and transactivation function of C protein from bacteriophage Mu
Author(s) -
Paul Bindu Diana,
Kanhere Aditi,
Chakraborty Atanu,
Bansal Manju,
Nagaraja Valakunja
Publication year - 2003
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.10413
Subject(s) - transactivation , biology , bacteriophage mu , gene , promoter , dna binding site , dna , sequence motif , dna binding domain , binding site , transcription factor , microbiology and biotechnology , hmg box , transcription (linguistics) , genetics , dna binding protein , bacteriophage , gene expression , linguistics , philosophy , escherichia coli
The C protein, a middle gene product of bacteriophage Mu, is the determinant of the transition from middle to late gene expression. C activates transcription from four late gene promoters, P lys , P I , P P , and P mom by binding to a site overlapping their −35 elements. Site‐specific, high‐affinity binding of C to its recognition sequence results in both axial and torsional distortion of DNA at P mom , which appears to play a role in recruitment of RNA polymerase to the promoter for mom gene transactivation. To identify the regions of C protein important for its function, deletion and site‐directed mutagenesis were carried out. We demonstrate here that a helix‐turn‐helix (HTH) motif located toward the carboxy terminal end of the protein is the DNA‐binding domain and amino acid residues involved in transactivation overlap the HTH motif. Mutagenesis studies also aided in the identification of the region important for dimerization. Structure‐based sequence alignment and molecular modeling in conjunction with mutational analysis suggest that the HTH motif is part of a three‐helix bundle, with remarkable similarity to paired (prd), a developmental regulatory protein from Drosophila . Additional key residues identified in the model to be crucial for C protein structure and DNA binding were shown to be important by mutagenesis. These results provide a structural framework for C function and insight into the mechanism of transactivation at the mom promoter. Proteins 2003;52:272–282. © 2003 Wiley‐Liss, Inc.