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KMID : 0620919960280040207
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Experimental & Molecular Medicine
1996 Volume.28 No. 4 p.207 ~ p.213
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Cloning and characterzation of a chicken protein tyrosine phosphatase, CPTP1
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Yoon Se Kang/Choong Won Kim
Eun Joo Jung/Yoon Se Kang
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Abstract
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Protein tyrosine phosphorylation and dephosphorylation are an important regulatory reactions in cell physiology. We have cloned a cDNA that encode a cytosolic protein tyrosine phosphatase (CPTP1) from chicken intestine cDNA library. Amino acid sequence identity between the CPTP1 and low molecular weight form of human placenta enzyme (HPTP1B) was 92%. CPTP1 lacked 13 amino acids in N-terminal region, while it had an additional 48 amino acids in the C-terminal region in comparison with the truncated form of HPTP1B of 321 amino acids. This C-terminal sequence was different from those of all known PTPs. The CPTP1 does not have a membrane targeting or nuclear localization sequences at its C-terminus like other PTPs such as HPTP1B and murine homolog of the human T-cell protein tyrosine phosphatase (MPTP) do. The cloned cDNA has been expressed in E. coli and purified by affinity chromatography. Dephosphorylation kinetics of this enzyme closely resembled those of the known PTPs. The dephosphorylation reaction required a reducing agent such as glutathione and dithiothreitol and was inhibited by sodium vanadate and formaldehyde. Deletion of 72 amino acids from C-terminal side of CPTP1 gene resulted in higher expression in E. coli and more potent phosphatase activity than wild type CPTP1 gene product. This result suggests that the C-terminal region of the CPTP1 protein negatively regulates phosphatase activity. These results also imply that CPTP1 might be a nontransmembrane-type enzyme with a structure and localization specificity distinct from other known cytosolic PTP1B type homolog.
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KEYWORD
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chicken, protein tyrosine phosphatase,
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