A Sequence Motif in the Transmembrane Region of Tyrosine Kinase Growth Factor Receptors

Abstract

The tyrosine kinase (TK) family of growth factor receptors (GFR) consists of one or more polypeptide chains organised into three regions; an N-terminal extracellular domain followed by a transmembrane section that leads to the intracellular domain e.g. (Hanks et al., 1988; Gullick, 1988). Ligand binding to the extracellular domain conveys the signal to the intracellular domain to induce its TK activity. This increase in TK activity then conveys the mitogenic stimulus to the nucleus promoting cell growth and division. The mechanism by which extracellular ligand binding stimulates intracellular TK activity is uncertain but there is considerable indirect evidence (e.g. Yarden and Schlessinger, 1987) that binding alters the conformation of the extracellular domain and promotes dimerisation of the receptors.