%0 Journal Article
%T Heterotrimeric G Proteins
%A Bahire K¨¹£¿¨¹kkaya
%A Beki Kan
%J T¨¹rk Biyokimya Dergisi
%D 2007
%I Turkish Biochemical Society
%X Heterotrimeric G proteins, commonly known as G proteins are members of thelarge GTPase superfamily that are conserved from bacteria to mammals. G proteinsplay an essential role in cellular signaling by coupling many cell surface receptorsto effectors on the plasma membrane. G proteins are composed of an ¦Á-subunit thatbinds and hydrolyzes GTP and a ¦Â¦Ã-subunit complex. To date over 20 different ¦Ásubunits, 5 ¦Â subunits and 14 ¦Ã subtypes have been defined. Classification of Gprotein heterotrimers are based on the primary sequences of their ¦Á-subunits, resultingin four main families. In its inactive state, each G protein is a heterotimer inwhich the GDP bound ¦Á chain is tightly associated with the ¦Â¦Ã subunits. Receptoractivation promotes the replacement of GDP by GTP and the consequent dissociationof ¦Á from ¦Â¦Ã. Both ¦ÁGTP and the ¦Â¦Ã complex interact with and regulate specificeffectors. Activation is then terminated by the intrinsic GTPase activity of the ¦Áchain, which returns the protein to its inactive state. G proteins are regulated byposttranslational modifications including phosphorylation, myristoylation, palmitoylation,and prenylation of G¦Á- and G¦Â¦Ã- subunits. G protein ¦Á- and ¦Â¦Ã- subunitsregulate the activities of diverse effectors. G proteins mediate a wide variety ofcellular responses, including sensory perception, neuronal activity and hormonalregulation. Recent reports indicate that GPCRs and G proteins are also involved inthe regulation of cell growth, differentiation and cellular transformation
%K Heterotrimeric G proteins
%K G proteins
%K cellular signaling
%U http://www.turkjbiochem.com/2007/039.pdf