E. E. Rusakova, A. P. Yankin, L. V. Memelova, V. L. Tunitskaya, and S. N. Kochetkov
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 117984 Russia;
E-mail: kochet@genome.eimb.relarn.ru
Received November 19, 1998
Abstract—The mutant forms of T7 RNA polymerase with the Met-635 and Ser-633 amino acid substitutions
in the conserved structural B motif were studied. The Met-635 mutation results in enzyme destabilization and
a sharp increase in the number of errors upon transcription. The Ser-633 mutation inactivates the polymerase
while its specific interaction with promoter is retained. As a whole, replacement of the amino acid residue at
position 633 has a more pronounced effect on the enzyme activity than that at position 635. The results obtained
show the importance of the sequence of hydroxy amino acid residues in motif B for the T7 RNA polymerase
activity.
Key words: RNA polymerase of T7 bacteriophage, B motif, mutant proteins, transcription
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