L. Marri et al., A putative sigma factor from Streptomyces sp. strain A21 can activate the expression of the cryptic operon bgl in Escherichia coli K-12, MOL G GENET, 261(1), 1999, pp. 201-207
Streptomyces sp A21 is a cellulolytic strain isolated from soil which was a
ssigned to the genus Streptomyces on the basis of distinctive morphological
features. A genomic library of A21 DNA has been constructed and transforme
d into Escherichia coli K-12 using a high-copy-number vector. One of the re
combinant plasmids activates the cryptic bgl operon when inserted into appr
opriate strains. The complete sequence of the 1629-bp A21 DNA fragment has
been determined. The analysis revealed the presence of an ORF whose putativ
e product shows a high degree of similarity to RNA polymerase sigma factors
; we therefore designated the gene psfS ((P) under bar utative (s) under ba
r igma (f) under bar actor, (S) under bar treptomyces). Mapping of the 5' t
erminus of transcript by primer extension indicated that PsfS induces trans
cription initiation within the bgl promoter-silencer region.