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J. Bacteriol., Jan 1996, 136-142, Vol 178, No. 1
Y Li and WR Strohl
We describe the isolation and characterization of a gene (ptpA) from
Streptomyces coelicolor A3(2) that codes for a protein with a deduced M(r)
of 17,690 containing significant amino acid sequence identity with
mammalian and prokaryotic small, acidic phosphotyrosine protein
phosphatases (PTPases). After expression of S. coelicolor ptpA in
Escherichia coli with a pT7-7-based vector system, PtpA was purified to
homogeneity as a fusion protein containing five extra amino acids. The
purified fusion enzyme catalyzed the removal of phosphate from p-
nitrophenylphosphate (PNPP), phosphotyrosine (PY), and a commercial
phosphopeptide containing a single phosphotyrosine residue but did not
cleave phosphoserine or phosphothreonine. The pH optima for PNPP and PY
hydrolysis by PtpA were 6.0 and 6.5, respectively. The Km values for
hydrolysis of PNPP and PY by PtpA were 0.75 mM (pH 6.0, 37 degrees C) and
2.7 mM (pH 6.5, 37 degrees C), respectively. Hydrolysis of PNPP by S.
coelicolor PtpA were 0.75 mM (pH 6.0, 37 degrees C) and 2.7 mM (pH 6.5, 37
degrees C), respectively. Hydrolysis of PNPP by S. coelicolor PtpA was
competitively inhibited by dephostatin with a Ki of 1.64 microM; the known
PTPase inhibitors phenylarsine oxide, sodium vanadate, and iodoacetate also
inhibited enzyme activity. Apparent homologs of ptpA were detected in other
streptomycetes by Southern hybridization; the biological functions of PtpA
and its putative homologs in streptomycetes are not yet known.
Copyright © 1996, American Society for Microbiology
Cloning, purification, and properties of a phosphotyrosine protein phosphatase from Streptomyces coelicolor A3(2)
Department of Microbiology, Ohio State University, Columbus 43210-1292, USA.
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