A mutational analysis of the structural basis for transcriptional activation and monomer-monomer interaction in the TyrR system of Escherichia coli K-12.
In response to the binding of tyrosine or phenylalanine, the TyrR protein (513 amino acids) activates certain promoters and represses others. In a previous study (J. Cui and R. L. Somerville, J. Bacteriol. 175:303-306, 1993), it was shown that promoter activation was selectively abolished in mutant proteins lacking amino acid residues 2 to 9. An additional series of constructs that encoded mutant TyrR proteins having deletions or point mutations near the N terminus were analyzed. Residues Arg-2 and Leu-3 were shown to be critical for the activation of the mtr promoter. In confirmation of previous findings, none of the activation-defective mutant TyrR proteins had lost significant repression function. The TyrR protein was shown by chemical cross-linking to be dimeric. The polypeptide segments critical for dimer formation in vivo were identified by evaluating the negative dominance phenotypes of a series of mutant proteins, all defective in DNA binding, lacking progressively greater numbers of amino acid residues from either the N terminus or the C terminus. Amino acid residues 194 to 438 were found to contain all of the essential dimerization determinants.
Cui
J
J
1153 Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153.
Somerville
R L
RL
D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015151:Immunoblotting; D007930:Leucine / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C069256:TyrR protein, E coli; D001120:Arginine; D007930:Leucine