Regulation of cellular signals by G-proteins

Extracellular signals are transduced across the cell by the cell surface receptors, with the aid of G-proteins, which act at a critical point of signal transduction and cellular regulation, Structurally, G-proteins are heterotrimeric consisting alpha, beta and gamma subunits but in functionally active state they dissociate into alpha subunit coupled to GTP and as beta gamma dimer. G-proteins can be broadly divided into two classes based on their sensitivity to pertussis toxin and cholera toxin. Existence of various forms of each of the subunit allows molecular diversity in the subunit species of G-proteins, These subunits interact with a wide range of receptors and effecters, facilitated by post translational modification of their subunits, Different types of G-proteins mediate several signalling events in different parts of the body, This review summarizes the features of (i) structural and functional heterogenity among different subunits of G-proteins, (ii) interaction of G-proteins and their subunits with effecters with specific cases of G-protein mediated signalling in olfaction, phototransduction in the retina, pas and uas related transduction and (iii) disease conditions associated with malfunctioning of G-proteins.