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J. Bacteriol., Jun 1997, 3619-3624, Vol 179, No. 11
LN Tieleman, GP van Wezel, MJ Bibb and B Kraal
The str operon of Streptomyces ramocissimus contains the genes for
ribosomal proteins S12 (rpsL) and S7 (rpsG) and for the polypeptide chain
elongation factors G (EF-G) (fus) and Tu (EF-Tu) (tuf). This kirromycin
producer contains three tuf or tuf-like genes; tuf1 encodes the regular
EF-Tu and is located immediately downstream of fus. In vivo and in vitro
transcription analysis revealed a transcription start site directly
upstream of S. ramocissimus tuf1, in addition to the operon promoter rpsLp.
Transcription from these promoters appeared to be growth phase dependent,
diminishing drastically upon entry into stationary phase and at the onset
of production of the EF-Tu-targeted antibiotic kirromycin. In surface-grown
cultures, a second round of tuf1 transcription, coinciding with aerial
mycelium formation and kirromycin production, was observed. The
tuf1-specific promoter (tuf1p) was located in the intercistronic region
between fus and tuf1 by high- resolution S1 mapping, in vitro
transcription, and in vivo promoter probing. During logarithmic growth, the
tuf1p and rpsLp transcripts are present at comparable levels. In contrast
to Escherichia coli, which has two almost identical tuf genes, the
gram-positive S. ramocissimus contains only tuf1 for its regular EF-Tu.
High levels of EF-Tu may therefore be achieved by the compensatory activity
of tuf1p.
Copyright © 1997, American Society for Microbiology
Growth phase-dependent transcription of the Streptomyces ramocissimus tuf1 gene occurs from two promoters
Department of Biochemistry, Leiden Institute of Chemistry, Leiden University, The Netherlands.
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