Signal transducing GTPases within animal and fungal cells

Signal transducing GTPases within animal and fungal cells 

Ras is known to be involved in the regulation of cellular proliferation and terminal differentiation [7,40]. In mammals, ras is activated by growth-factor-receptor tyrosine kinases and other tyrosine kinases. Some of these kinases phosphorylate the She protein and phosphorylated She plus autophosphorylated receptor proteins bind the SH2 domain 

Many other proteins closely related to ras are now known and are considered as members of the ras superfamily which numbers 100 members. Within this superfamily are several subgroups, with Ras being joined by the Ran/Rac, Ypt/Rab and Rho proteins. The cellular functions of these proteins are exceedingly diverse including such processes as vesicular trafficking, cytoskeletal control and NADPH oxidase function. Clearly, such important proteins have plant homologues which will be discussed later. 

Heterotrimeric G-proteins A number of excellent reviews are already extant concerning the heterotrimeric G-protein family covering topic areas on their structure, molecular connections and functions [16,23,24,33,34,37,44,49,53,73,87,107,125,140]. In the present review we shall only attempt to give an overview. 

Operationally, the heterotrimeric G-proteins function by means of a well defined catalytic cycle (Fig. 1). In this, the de-binding of GDP followed by the subsequent binding 

---