The exsitence of GTP binding regulatory proteins (for short term, often refered as G proteins) in higher plant cells is certain. G proteins are classified into two groups based on their molecular structures, which are the heterotrimeric G proteins (big G proteins) that contain three different subunits and the small G proteins that have only one subunit (monomeric G proteins). All G proteins are characterized by their properties to bind with and hydrolyze GTP, by which G proteins function as transmembrane and intracellular signalling molecules. As a distinguished participant in signal transduction, G proteins directly and/or indirectly regulate a number of physiological processes, such as regulation of phytochrome related physiological processes and gene expression, involvement in blue light response, K + channel regulation, stomatal movement, hormone regulation, protein phosphrylation/dephosphorylation, etc. Although G proteins in plant cells have not been purified, the genes for α subunit of heterotrimeric G proteins have been cloned. More evidences for the importance of G proteins in plant signalling processes are rapidly accumulating.
展开▼
