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

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.

Mechanism of the CO-sensing heme protein CooA: new insights from the truncated heme domain and UVRR spectroscopy.

The bacterial CO-sensing heme protein CooA activates expression of genes whose products perform CO-metabolism by binding its target DNA in response to CO binding. The required conformational change has been proposed to result from CO-induced displacement of the heme and of the adjacent C-helix, which connects the sensory and DNA-binding domains. Support for this proposal comes from UV Resonance Raman (UVRR) spectroscopy, which reveals a more hydrophobic environment for the C-helix residue Trp110 when CO binds.

The role of the DNA-binding domains in CooA activation.

Carbon monoxide oxidation activator protein (CooA) is a dimeric carbon monoxide (CO) binding transcription factor that in the presence of CO promotes the transcription of genes involved in CO oxidation in Rhodospirillum rubrum. The off state (inactive) of Fe(II) CooA has His and Pro as the two axial heme ligands. In contrast, in the on state, which is active in DNA binding, the Pro ligand bond has been replaced by CO.