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This article is part of the supplement: 5th International Conference on cGMP: Generators, Effectors and Therapeutic Implications

Open Access Poster presentation

A structural analysis of the regulatory domain from the cGMP-dependent protein kinase Iα

Brent W Osborne1*, Andrew T Menke1, Donald K Blumenthal2 and Wolfgang R Dostmann1

Author Affiliations

1 Department of Pharmacology, College of Medicine, University of Vermont, Burlington, VT 05405, USA

2 Department of Pharmacology & Toxicology, University of Utah, Salt Lake City, Utah 84112, USA

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BMC Pharmacology 2011, 11(Suppl 1):P53  doi:10.1186/1471-2210-11-S1-P53

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2210/11/S1/P53


Published:1 August 2011

© 2011 Osborne et al; licensee BioMed Central Ltd.

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background

The cGMP-dependent protein kinase (PKG) has two tandem cyclic nucleotide binding (CNB) domains which act as the primary intracellular receptor for cGMP [1,2]. PKG exhibits a homodimeric rod-like structure which undergoes significant molecular rearrangements upon the binding of cGMP [3-5]. However, a detailed structural analysis of the core regulatory elements inherent to PKG is still required.

Results

We recently solved a crystal structure of the two cGMP binding sites from PKG Iα in order to highlight the atomic details of the regulatory domain. This PKG78-355 structure is free of cGMP and presents the protein in an elongated conformation. A surprising dimeric arrangement between PKG78-355 protomers is orchestrated via hydrophobic contacts between a novel helical element C-terminal to the second cGMP binding site (the switch helix) and the opposite CNB domain B (Figure 1). Small angle X-ray scattering (SAXS) of PKG78-355 suggests an overall molecular dimension of ~130 Å, consistent with the maximal linear dimension observed in our crystal structure. Upon incubation with cGMP, PKG78-355 contracted to ~95 Å. This molecular compaction was not observed in a construct lacking the switch helix (PKG78-326), suggesting the additional importance of the switch helix in mediating cGMP-specific conformational changes inherent to the regulatory domain.

thumbnailFigure 1. Overall fold of PKG78-355. The crystal structure of the PKG regulatory domain identifies a novel allosteric interface between PKG78-355 protomers.

Conclusion

Overall, these studies provide the first atomic resolution model of tandem cGMP binding domains and expand our understanding of the allosteric mechanisms surrounding PKG activation.

References

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