Abstract
We have cloned human protein kinase Bgamma (PKBgamma) and found that it contains two regulatory phosphorylation sites, Thr305 and Ser472, which correspond to Thr308 and Ser473 of PKBalpha. Thus it differs significantly from the previously published rat PKBgamma. We have also isolated a similar clone from a mouse cDNA library. In human tissues, PKBgamma is widely expressed as two transcripts. A mutational analysis of the two regulatory sites of human PKBgamma showed that phosphorylation of both sites, occurring in a phosphoinositide 3-kinase-dependent manner, is required for full activity. Our results suggest that the two phosphorylation sites act in concert to produce full activation of PKBgamma, similar to PKBalpha. This contrasts with rat PKBgamma, which is thought to be regulated by 3-phosphoinositide-dependent protein kinase 1 alone.
Highlights
Three members of the protein kinase B (PKB)1 subfamily of second-messenger regulated serine/threonine protein kinases have been identified and termed ␣, , and ␥ (1– 4)
Screening of several human cDNA libraries led to the isolation of 12 clones encoding partial and overlapping sections of the open reading frame of human PKB␥, and the cDNA was
The 479-residue amino acid sequence of human PKB␥ is presented in Fig. 1, as an alignment with human PKB␣, PKB, mouse PKB␥, and with the C-terminal domain of rat PKB␥
Summary
Three members of the protein kinase B (PKB)1 subfamily of second-messenger regulated serine/threonine protein kinases have been identified and termed ␣, , and ␥ (1– 4). Phosphorylation of PKB␣/ occurs on two regulatory sites, Thr308/309 in the activation loop in the catalytic domain and
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