Analysis of G-Proteins Regulating Signal Transduction Pathways

Abstract

Part A. Identification of G-Proteins

The past decade has seen the emergence of a rapidly expanding superfamily of regulatory proteins, the G-proteins, that transduce as diverse a range of biological functions as protein synthesis, transmembrane signaling, intracellular trafficking, and cell proliferation (reviewed in 1). The application of biochemical and molecular biological techniques has substantially increased our understanding of the structure and function of G-proteins and has revealed a highly conserved primary structure and molecular mechanism throughout evolution. The central mechanistic concept is that G-proteins can exist in two interconvertible conformational states, one inactive (GDP-bound) and one active (GTP-bound). This basic cycle of GTP binding and hydrolysis (by an intrinsic GTPase) can confer both directionality and amplification to G-protein-mediated events. Although novel individual species have recently been identified (e.g., 2), there are presently three major classes of G-proteins