The structural determinants of PH domain-mediated regulation of Akt revealed by segmental labeling

Akt is a critical protein kinase that governs cancer cell growth and
metabolism. Akt appears to be autoinhibited by an intramolecular
interaction between its N-terminal pleckstrin homology (PH) domain and
kinase domain, which is relieved by C-tail phosphorylation, but the
precise molecular mechanisms remain elusive. Here we use a combination of
protein semisynthesis, NMR, and enzymological analysis to characterize
structural features of the PH domain in its autoinhibited and activated
states. We find that Akt autoinhibition depends on the length/tension of
the PH-kinase linker. We identify a role for a dynamic short segment in
the PH domain that appears to regulate autoinhibition and PDK1-catalyzed
phosphorylation of Thr308 in the activation loop. We determine that Akt
allosteric inhibitor MK2206 drives distinct PH domain structural changes
compared to baseline autoinhibited Akt. These results highlight how the
conformational plasticity of Akt governs the delicate control of its
catalytic properties.