Protein kinase B beta (PKB-beta), also known as AKT2, is one of three closely related serine/threonine-protein kinases: AKT1/alpha, AKT2/beta and AKT3/gamma. PKBs contain an N-terminal pleckstrin homology (PH) domain and a C-terminal catalytic domain []. PKB-beta is the predominant PKB isoform expressed in insulin-responsive tissues. It plays a critical role in the regulation of glucose homeostasis []. It is also implicated in muscle cell differentiation []. Mice deficient in PKB-beta display normal growth weights but exhibit severe insulin resistance and diabetes, accompanied by lipoatrophy and B-cell failure [].
Protein kinase B (PKB), also called Akt or RAC, is a phosphatidylinositol 3'-kinase (PI3K)-dependent Ser/Thr kinase which alters the activity of the targeted protein []. Akt regulates numerous cellular processes, including cell growth, differentiation, proliferation, apoptosis, and glucose metabolism. Among its many roles, Akt appears to be common to signaling pathways that mediate the metabolic effects of insulin in several physiologically important target tissues [, ]. Human Akt has three isoforms derived for distinct genes: Akt1/PKBalpha, Akt2/PKBbeta, and Akt3/PKBgamma.This entry includes the isoforms alpha. Akt1 and Akt2 have distinct functions; they are involved in the control of growth and metabolism, respectively [, ].
Potassium channels take part in important processes of higher plants, including opening and closing of stomatal pores and leaf movement. Inward rectifying potassium (K(+)in) channels play an important role in turgor regulation and ion uptake in higher plants. All of them comprise, from their N-terminal to their C-terminal ends: a short hydrophilic region, a hydrophobic region structurally analogous and partially homologous to the transmembrane domain of voltage-gated animal channels from the Shaker superfamily, a putative cyclic nucleotide-binding domain, and a conserved C-terminal KHA domain. Between these last two regions, some of them (AKT1, AKT2 and SKT1) contain an ankyrin-repeat domain with six repeats homologous to those of human erythrocyte ankyrin. This entry represents the KHA domain which is unique to plant K(+)in channels. The KHA domain contains two high-homology blocks enriched for hydrophobic and acidic residues, respectively. The KHA domain is essential for interaction of plant K(+)in channels. The KHA domain mediates tetramerization and/or stabilisation of the heteromers [, , ].
