title: Isolation and characterization of mutant bacteriophage T7 RNA polymerases.
abstract: 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.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, PA 15260.
authors.forename: D
authors.initials: D
authors.lastname: Patra
authors.forename: E M
authors.initials: EM
authors.lastname: Lafer
authors.forename: R
authors.initials: R
authors.lastname: Sousa
mesh_terms: D002384:Catalysis; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D016296:Mutagenesis; D009154:Mutation; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D013329:Structure-Activity Relationship; D013604:T-Phages / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D012321:DNA-Directed RNA Polymerases