Volume 270,
Number 20,
Issue of May 19, pp. 12319-12326, 1995
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
Virginiae
Butanolide Binding Protein from Streptomyces virginiae
EVIDENCE THAT VbrA IS NOT THE VIRGINIAE BUTANOLIDE BINDING
PROTEIN AND REIDENTIFICATION OF THE TRUE BINDING PROTEIN
Susumu
Okamoto
,
Kenji
Nakamura
,
Takuya
Nihira
,
Yasuhiro
Yamada
Virginiae butanolides (VBs) A-E are butyrolactone
autoregulators that control virginiamycin production in
Streptomyces virginiae. We have previously reported the
purification and molecular cloning of VbrA, a putative VB binding
protein (Okamoto, S., Nihira, T., Kataoka, H., Suzuki, A., and Yamada,
Y.(1992) J. Biol. Chem. 267, 1093-1098). However, VbrA
protein overexpressed in Escherichia coli did not show any
detectable VB binding activity nor did the immunoprecipitation of
native VbrA from a cell-free extract of S. virginiae cause any
decrease in such activity, indicating that VbrA is not the true VB
binding protein. This finding prompted us to seek the true VB binding
protein by repurification. After successive purification by anion
exchange, gel filtration, heparin, and hydrophobic interaction
chromatography, a 26-kDa protein (p26k) was identified as the true VB
binding protein. Partial amino acid sequences of p26k were determined,
and the gene (barA) that encodes this protein was isolated and
cloned using degenerate oligonucleotide probes. When the barA gene was expressed in Streptomyces lividans and E.
coli, strong VB binding activity appeared, demonstrating
unambiguously that the S. virginiae p26k protein is the true
VB binding protein.