Isolation and characterization of mutant bacteriophage T7 RNA polymerases

Debabrata Patra, Eileen M. Lafer, Rui Sousa

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We have isolated and characterized a number of bacteriophage T7 RNAP (RNA polymerase) null mutants. Most of the mutants found to be completely inactive in vitro map to one of the well-conserved blocks of residues in the family of RNAPs homologous to T7 RNAP. The in vitro phenotypes of a smaller number of partially active T7 RNAP mutants, mapping outside these well-conserved regions, support the following assignment of functions in T7 RNAP: (1) the N-terminal region of T7 RNAP contains a nascent RNA binding site that functions to retain the nascent chain within the ternary complex; (2) the region surrounding residue 240 is involved in binding the initiating NTP; (3) residues at the very C terminus of T7 RNAP are involved in binding the elongating NTP.

Original languageEnglish
Pages (from-to)307-318
Number of pages12
JournalJournal of Molecular Biology
Issue number2
StatePublished - Mar 20 1992


  • T7 RNA polymerase
  • bacteriophage RNA polymerase
  • mutagenesis
  • transcription mechanisms


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