Effects of Amino Acid Substitutions at Conserved and Acidic Residues within Region 1.1 of Escherichia coli ς(70)

Amino acid substitutions in Escherichia coli ς(70) were generated and characterized in an analysis of the role of region 1.1 in transcription initiation. Several acidic and conserved residues are tolerant of substitution. However, replacement of aspartic acid 61 with alanine results in inactivity caused by structural and functional thermolability.