Liakhov D L, Il'genfrits Kh, Chernov B K, Dragan S M, Rechinskiĭ V O, Pokholok D K, Tunitskaia V L, Kochetkov S N
Mol Biol (Mosk). 1992 Sep-Oct;26(5):1022-35.
Lys-172 residue of bacteriophage T7 RNA polymerase (T7RP) was substituted for Leu and Gly and Lys-172, Arg-173 were deleted by the site-directed mutagenesis using synthetic oligonucleotides. The specific activity of all mutant enzymes did not differ significantly from that of the wild-type (w.t.) T7RP while for Gly-172 mutant (G172) it was somewhat lower. Leu-172 (L172) and deletion (DEL172-3) mutants were able to direct RNA synthesis on the templates lacking the T7 promoter. DEL172-3 was not able to synthesize extraneous RNA sequences in addition to the expected run-off transcripts. L172 and DEL172-3 mutants revealed altered template specificity toward various DNA templates and showed the lower stability of enzyme-promoter complexes. The possible role of Lys-172 likely belonging to an interdomain "stretch" is discussed.
利用合成寡核苷酸通过定点诱变将噬菌体T7 RNA聚合酶（T7RP）的第172位赖氨酸残基替换为亮氨酸和甘氨酸，并删除了第172位赖氨酸和第173位精氨酸。所有突变酶的比活性与野生型（w.t.）T7RP相比无显著差异，而甘氨酸-172突变体（G172）的比活性略低。亮氨酸-172（L172）和缺失（DEL172-3）突变体能够在缺乏T7启动子的模板上指导RNA合成。DEL172-3除了预期的径流转录本外，无法合成额外的RNA序列。L172和DEL172-3突变体对各种DNA模板的模板特异性发生了改变，并且酶-启动子复合物的稳定性较低。讨论了可能属于域间“延伸”的第172位赖氨酸的作用。
