Higher plant tyrosine-specific protein phosphatases (PTPs) contain novel amino-terminal domains: expression during embryogenesis
Higher plant tyrosine-specific protein phosphatases (PTPs) contain novel amino-terminal domains: expression during embryogenesis
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DOI：
10.1023/a:1006170902271
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发表时间：
1999-02-01
影响因子：
5.1
通讯作者：
Gatehouse, JA
中科院分区：
文献类型：
--
作者：
Fordham-Skelton, AP;Skipsey, M;Gatehouse, JA
已经在拟南芥、大豆和豌豆中鉴定了编码与蛋白酪氨酸磷酸酶具有同源性的蛋白质的序列。每个包含一个预测的催化结构域含有酪氨酸特异性蛋白磷酸酶（PTPs）的特征序列基序，在其他真核生物的信号转导中发挥重要作用，并从双特异性，cdc 25或低分子量蛋白酪氨酸磷酸酶不同。通过表征表达为重组His标记的融合蛋白的大豆PTP来确认它们作为PTP的身份。该酶对对硝基苯酚磷酸（pNPP）和磷酸酪氨酸具有磷酸酶活性，但不能以可测量的速率水解磷酸丝氨酸或磷酸苏氨酸。含有磷酸酪氨酸的肽也充当底物，K-m值在微摩尔范围内。活性被酪氨酸磷酸酶特异性抑制剂（钒酸盐，dephostatin）废除，但不受丝氨酸/苏氨酸蛋白磷酸酶抑制剂（氟化物，矢车菊苷，金属螯合剂）。凝胶过滤层析表明重组酶为单体。拟南芥PTP序列作为基因组克隆和部分EST分离，而豌豆和大豆序列作为cDNA分离。Southern分析表明，拟南芥中存在单个基因，豌豆和大豆中存在一个小基因家族。在豌豆中，PTP转录本存在于胚胎中，并随着发育水平降低;转录本在其他组织中也可检测到。植物PTP都含有一个相似的N-末端结构域，其与任何已知的蛋白质序列都没有相似性。该结构域可能参与植物特有的PTP功能。
Sequences encoding proteins with homology to protein tyrosine phosphatases have been identified in Arabidopsis, soybean and pea. Each contains a predicted catalytic domain containing sequence motifs characteristic of tyrosine-specific protein phosphatases (PTPs) which play an important role in signal transduction in other eukaryotes and are distinct from dual-specificity, cdc25 or low-molecular-weight protein tyrosine phosphatases. Their identity as PTPs was confirmed by characterising the soybean PTP expressed as a recombinant His-tagged fusion protein. The enzyme had phosphatase activity towards p-nitrophenolphosphate (pNPP) and phosphotyrosine, but did not hydrolyse phosphoserine or phosphothreonine at a measureable rate. Phosphotyrosine containing peptides also served as substrates, with K-m values in the micromolar range. Activity was abolished by inhibitors specific for tyrosine phosphatases (vanadate, dephostatin) but was unaffected by inhibitors of serine/threonine protein phosphatases (fluoride, cantharidin, metal-chelating agents). Gel filtration chromatography showed that the recombinant enzyme was a monomer. The Arabidopsis PTP sequence was isolated both as a genomic clone and as a partial EST, whereas the pea and soybean sequences were isolated as cDNAs. Southern analysis suggested a single gene in Arabidopsis and a small gene family in pea and soybean. In pea, PTP transcripts were present in embryos, and decreased in level with development; transcripts were also detectable in other tissues. The plant PTPs all contain a similar N-terminal domain which shows no similarity to any known protein sequence. This domain may be involved in PTP functions unique to plants.