[Study of the form of bacteriophage T7 RNA polymerase containing point substitutions in the region of functionally important amino acid residues].

A study was carried out on the influence of point mutations of the functional amino acid residues on the secondary and ternary structure of bacteriophage T7 RNA polymerase as well as on the activity of the enzyme. A change in residue 631 is accompanied by significant changes in secondary structure (alpha-->beta transition). The substitution Lys-172 Leu changes both the secondary and ternary structures whereas the deletion of residues 172-173 does not lead to such changes. Changes in residues 631-632 do not affect the ability of the enzyme to bind the promoter and/or the synthesis of a full-length transcript but disturbs phosphodiester bond formation.