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AKT (Akt1, Akt2 and Akt3)/PKB & CTMP Antibodies
Putative human homologs of the protooncogene v-akt of the acutely transforming retrovirus AKT8 have been cloned. These protein-serine/threonine kinase proteins have a catalytic domain closely related to both PKA and PKC and have been designated rac (related to A and C kinases), pkb (Protein kinase B) or Akt. RAC protein kinase family members feature pleckstrin homology (PH) domain at the amino terminus and a protein-serine/threonine kinase catalytic domain at the carboxy terminus. The Amino terminal domain (referred to as AH-Akt Homology domain) spans from 1-148 amino acids and contains the PH domain, a region found in diverse group of signaling proteins. The PH domain (amino acids 1-106) has been implicated in interactions with other proteins such as G-protein bg subunits, as well as phosphoinositides. The kinase domain is located between residues 148 to 411. These enzymes are activated by diverse ligands such as PGDF, EGF and basic FG in NIH 3T3, Rat-1 or Swiss-3T3 cells. AKT1 (RAC-PK-a or PKB-a) is the human homolog of v-akt and is identical to RAC gene. The protein has been observed to show different migratory patterns on a western blot according to the state of phosphorylation of the protein. Phosphatase treatment has been shown to result in inactivation of the protein. AKT2 (RAC-PK-b) has
been shown to be amplified and over-expressed in some human carcinoma cell lines
and primary tumors suggesting that it may contribute to the development of
common epithelial tumors of the ovary. It has been reported that anti-sense AKT2
can greatly inhibit the expression of AKT2 protein and AKT3 or Protein Kinase gamma (RAC-PK-g) is highly related to other members of RAC protein kinase family. It is abundantly expressed in testes and brain and is involved in regulation of cellular growth. Studies to date suggest that Pleckstrin homology domains of RAC protein kinase family could associate with more than one protein for regulation of activity or distribution of this enzyme family by different ways. Protein kinase B (PKB) is a major downstream
target of receptor tyrosine kinases that signal via phosphatidylinositol
3-kinase (PIK3). Upon cell stimulation, PKB is translocated to the plasma
membrane, where it is phosphorylated on thr308 in
the catalytic domain and ser473 in the C-terminal
regulatory domain. Several protein partners for PKB have been identified.
CTMP, a carboxyl terminal modulator protein, binds
to PKB-alpha and negatively regulates PKB activity by inhibiting phosphorylation
of these PKB residues. CTMP (mouse 248-aa, human 240-aa, chromosome 1q21, 22-26
kDa) predominantly expressed in skeletal muscle, testis, uterus, brain, and
kidney, with lower levels in heart, liver, and lung. The presence of multiple
transcripts suggested that CTMP undergoes alternative splicing.
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