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J. Bacteriol., 11 1995, 6083-6092, Vol 177, No. 21
H Onaka, N Ando, T Nihira, Y Yamada, T Beppu and S Horinouchi
A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) and its
specific receptor protein control streptomycin production, streptomycin
resistance, and aerial mycelium formation in Streptomyces griseus. The
A-factor receptor protein (ArpA) was purified from a cell lysate of S.
griseus IFO 13350. The NH2-terminal amino acid sequences of ArpA and lysyl
endopeptidase-generated fragments were determined for the purpose of
preparing oligonucleotide primers for cloning arpA by the PCR method. The
arpA gene cloned in this way directed the synthesis of a protein having
A-factor-specific binding activity when expressed in Escherichia coli under
the control of the T7 promoter. The arpA gene was thus concluded to encode
a 276-amino-acid protein with a calculated molecular mass of 29.1 kDa, as
determined by nucleotide sequencing. The A-factor-binding activity was
observed with a homodimer of ArpA. The NH2-terminal portion of ArpA
contained an alpha-helix-turn-alpha-helix DNA-binding motif that showed
great similarity to those of many DNA- binding proteins, which suggests
that it exerts its regulatory function for the various phenotypes by
directly binding to a certain key gene(s). Although a mutant strain
deficient in both the ArpA protein and A-factor production overproduces
streptomycin and forms aerial mycelium and spores earlier than the
wild-type strain because of repressor-like behavior of ArpA, introduction
of arpA into this mutant abolished simultaneously its streptomycin
production and aerial mycelium formation. All of these data are consistent
with the idea that ArpA acts as a repressor-type regulator for secondary
metabolite formation and morphogenesis during the early growth phase and
A-factor at a certain critical intracellular concentration releases the
derepression, thus leading to the onset of secondary metabolism and aerial
mycelium formation. The presence of ArpA-like proteins among Streptomyces
spp., as revealed by PCR, together with the presence of A- factor-like
compounds, suggests that a hormonal control similar to the A-factor system
exists in many species of this genus.
Copyright © 1995, American Society for Microbiology
Cloning and characterization of the A-factor receptor gene from Streptomyces griseus
Department of Biotechnology, University of Tokyo, Japan.
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