Nucleic Acids Research, Vol 24, Issue 22 4565-4571, Copyright © 1996 by Oxford University Press
EJ Cho, JB Bae, JG Kang and JH Roe
The rpoA gene, encoding the alpha subunit of RNA polymerase, was cloned
from Streptomyces coelicolor A3(2). It is preceded by rpsK and followed by
rplQ, encoding ribosomal proteins S11 and L17, respectively, similar to the
gene order in Bacillus subtilis. The rpoA gene specifies a protein of 339
amino acids with deduced molecular mass of 36,510 Da, exhibiting 64.3 and
70.7% similarity over its entire length to Escherichia coli and B. subtilis
alpha subunits, respectively. Using T7 expression system, we overexpressed
the S. coelicolor alpha protein in E. coli. A small fraction of this
protein was found to be assembled into E. coli RNA polymerase. Antibody
against S. coelicolor alpha protein crossreacted with that of B. subtilis
more than with the E. coli alpha subunit. The ability of recombinant alpha
protein to assemble beta and beta' subunits into core enzyme in vitro was
examined by measuring the core enzyme activity. Maximal reconstitution was
obtained at alpha2:beta+beta' ratio of 1:2.3, indicating that the
recombinant alpha protein is fully functional for subunit assembly. Similar
results were also obtained for natural alpha protein. Limited proteolysis
with endoproteinase Glu-C revealed that S. coelicolor alpha contains a
tightly folded N-terminal domain and the C-terminal region is more
protease-sensitive than that of E. coli alpha.
ARTICLES
Molecular analysis of RNA polymerase alpha subunit gene from Streptomyces coelicolor A3(2)
Department of Microbiology, College of Natural Sciences, Seoul National University, Korea.
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