Premium
The molar ratio of σ 73 to core polymerase in the obligate intracellular bacterium, Rickettsia prowazekii
Author(s) -
Ding HanFei,
Winkler Herbert H.
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb00365.x
Subject(s) - rickettsia prowazekii , biology , rna polymerase , microbiology and biotechnology , sigma factor , polymerase , biochemistry , escherichia coli , virology , enzyme , gene , rickettsia , virus
Summary In the obligate Intracellular parasitic bacterium, Rickettsia prowazekii, the molar ratio of σ 73 to core RNA polymerase, that is, the degree of saturation of the core polymerase by the catalytically active sigma factor, was very low. This ratio was determined from the radioactivity in rickettsial RNA polymerase immuno‐precipitated from crude extracts of infected L929 cells in which the parasite was exponentially growing. If we assume that, as Is true for the σ subunit, in R. prowazekii and Escherichia coli the β’and β subunits of the RNA polymerase have similar methionine and cysteine contents (the radiolabelled amino acids), the molar ratio of σ 73 to core polymerase in R prowazekii would be 0.1. This is in striking contrast to E. Coli where the ratio is typically 0.4. it remains to be established whether this low sigma saturation results In a limitation of active RNA polymerase in R. prowazekii and contributes to its slow growth.