Seger R, Yarden Y, Kashles O, Goldblatt D, Schlessinger J, Shaltiel S
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
J Biol Chem. 1988 Mar 5;263(7):3496-500.
A brush-border membranal proteinase, which specifically clips the catalytic subunit of cAMP-dependent protein kinase, is shown to cleave the receptor for the epidermal growth factor (EGF) (Mr = 170,000) into two fragments of Mr = 140,000 and 30,000. The 140-kDa fragment retains its EGF-binding site and its EGF-dependent protein tyrosine kinase activity on exogenous substrates, but it loses its capacity to undergo self-phosphorylation. It is shown to be distinct from the 150-kDa fragment of the EGF receptor obtained by the Ca2+-activated neutral proteinase. The membranal proteinase strictly recognizes the native structure of the receptor and fails to cleave either the denatured receptor or its 150-kDa degradation product. Thus the membranal proteinase acts as a conformation-recognizing probe for both the protein-tyrosine kinase domain of the EGF receptor and the catalytic subunit of cAMP-dependent protein-Ser/Thr kinase, suggesting that the known sequence homology between these two kinases is also reflected in their conformation. The well defined 140-kDa fragment described here is useful for structure-function studies of the EGF receptor.
一种刷状缘膜蛋白酶，它能特异性地剪切环磷酸腺苷（cAMP）依赖性蛋白激酶的催化亚基，已被证明可将表皮生长因子（EGF）受体（分子量 = 170,000）切割成分子量分别为140,000和30,000的两个片段。140 kDa的片段保留了其EGF结合位点以及在外源底物上的EGF依赖性蛋白酪氨酸激酶活性，但失去了自我磷酸化的能力。已证明它与通过Ca2+激活的中性蛋白酶获得的EGF受体150 kDa片段不同。膜蛋白酶严格识别受体的天然结构，无法切割变性受体或其150 kDa的降解产物。因此，膜蛋白酶可作为EGF受体蛋白酪氨酸激酶结构域和cAMP依赖性蛋白 - 丝氨酸/苏氨酸激酶催化亚基的构构构象识别探针，这表明这两种激酶之间已知的序列同源性也反映在它们的构象上。这里描述的明确的140 kDa片段对于EGF受体的结构 - 功能研究很有用。
