Studies on the functions of the RNA polymerase components by means of mutations

Temperature-sensitive RNA polymerase mutants with altered subunit synthesis and degradation.

“…These combined resultst allowved us to assign group I) to the cistron encoding the (3 subunit of RNA polyrmerase, and group E to a cistron corresj)on(ling to another gene in the same operon. Group E mutations also failed to complement TsX, a teml)erature-sensitive RNA l)0ymerase mutation isolated by Khesin et al (8) which is known to be a is'mutation as shown by the in vitro reconstitution of the RNA polymerase from purified subunits (9). We, therefore, have assigned complemnentation group E to the structural gene for Olt.…”

“…4A shows that at 300, A2R7 synthesizes both /3 and ,/' at a slightly higher rate than wild-type, and that these subunits are degraded with half-lives of about 63 and 35 min, respectively. Fifteen minutes after the culture is shifted to 420, not only does this mutant appear to synthesize both subunits at a 2-to 3-fold lower rate than at 300, but also it degrades both subunits with a half-life of about 8 quently, by 20-30 min after pulse-labeling at 420, there are no significant amounts of either labeled 13 or 13' present in the cell (see also Fig. 3A).…”

Rifamycins: A General View

“…Single-step mutants with different levels of resistance can be isolated varying from slightly to highly resistant (>2000 ,ug/ml). All resistant mutants (whatever the level of resistance) from which an RNA polymerase has been purified, possess a modified enzyme that is more resistant to the drug when tested in vitro (48,49,(78)(79)(80)(81)(82)(83)(84)(85)(86)(87)(88)(89)(90). The majority of these data were obtained with Escherichia coli.…”

“…All the rifampicin-resistant mutants that have been mapped in E. coli ei ther by conjugation (78)(79)(80)(82)(83)(84)(85)(86)(87) or by transduction (48,49,101), are located near the arg H locus. Temperature-sensitive mutants have.…”

Subunit topography of RNA polymerase (E. coli) in the complex with DNA

“…3) the tsX mutation (in E. Coli strains T16 and Tsl9) which affects the binding of the enzyme to the template has been located in 8' subunit (35)(36). 4) the binding of poly [d(A-Tj] protects about 10 lysyl c-amino groups of the holoenzyme as determined by fluorescamine (37) which are preferentially located on 8' and 8 subunits.…”