Coupling of ras to the T Cell Antigen Receptor
The ras proto-oncogenes, Ha-, Ki- and N-ras, encode 21-kDa GTPases that are critical regulatory proteins in all eukaryotic cells. In most mammalian cell types, ras proteins are essential for cell growth and when constitutively activated by point mutation cause cellular transformation. In some cell types ras proteins have been implicated in differentiation pathways. Their activity is normally regulated by a cycle of binding GTP to give the biologically active form of the protein followed by hydrolysis of bound GTP to GDP. The GDP bound form of the protein is inactive: it is reactivated by exchange of bound GDP for free cytosolic GTP (see other chapters in this volume).
KeywordsNerve Growth Factor Phorbol Ester Cell Antigen Receptor P21ras Protein Critical Regulatory Protein
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