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Structural basis for the regulation of protein kinase A by activation loop phosphorylation.


ABSTRACT: The catalytic subunit of cAMP-dependent protein kinase (PKA) is a member of the AGC group of protein kinases. Whereas PKA has served as a structural model for the protein kinase superfamily, all previous structures of the catalytic subunit contain a phosphorylated activation loop. To understand the structural effects of activation loop phosphorylation at Thr-197 we used a PKA mutant that does not autophosphorylate at Thr-197. The enzyme crystallized in the apo-state, and the structure was solved to 3.0 Å. The N-lobe is rotated by 18° relative to the wild-type apoenzyme, which illustrates that the enzyme likely exists in a wide range of conformations in solution due to the uncoupling of the N- and C-lobes. Several regions of the protein including the activation loop are disordered in the structure, and there are alternate main chain conformations for the magnesium positioning loop and catalytic loop causing a complete loss of hydrogen bonding between these two active site structural elements. These alterations are reflected in a 20-fold decrease in the apparent phosphoryl transfer rate as measured by pre-steady-state kinetic methods.

SUBMITTER: Steichen JM 

PROVIDER: S-EPMC3340281 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Structural basis for the regulation of protein kinase A by activation loop phosphorylation.

Steichen Jon M JM   Kuchinskas Michael M   Keshwani Malik M MM   Yang Jie J   Adams Joseph A JA   Taylor Susan S SS  

The Journal of biological chemistry 20120210 18


The catalytic subunit of cAMP-dependent protein kinase (PKA) is a member of the AGC group of protein kinases. Whereas PKA has served as a structural model for the protein kinase superfamily, all previous structures of the catalytic subunit contain a phosphorylated activation loop. To understand the structural effects of activation loop phosphorylation at Thr-197 we used a PKA mutant that does not autophosphorylate at Thr-197. The enzyme crystallized in the apo-state, and the structure was solved  ...[more]

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