# Conjoined NO-sensitive guanylyl cyclases

Sönke Behrends*, Mareike Busker, Nadine Haase, Tobias Haase, Jan Krähling, Monika Linnenbaum

*From* 5th International Conference on cGMP: Generators, Effectors and Therapeutic Implications
Halle, Germany. 24-26 June 2011

## Background

NO-sensitive guanylyl cyclases (NO-GC's) that catalyze the reaction of GTP to the second messenger molecule cGMP are heterodimeric enzymes consisting of an α and a β₁ subunit. The two prevalent isoforms in humans (α₁/β₁, α₂/β₁) are time-tested targets for drugs that release nitric oxide (NO) and new compounds that either sensitize the enzyme for activation by NO or activate the enzyme independently of NO. Homologous NO-GC subunits consist of an amino-terminal HNOX domain followed by a PAS- and a coiled coil domain and the carboxy-terminal catalytic domain.

## Results

Measurement of FRET between fluorescent proteins tagged to the amino- and carboxy-terminus of the subunits indicated close proximity between the amino-terminal HNOX domains and the carboxy-terminal catalytic domains of the enzyme. On the basis of these results we constructed conjoined NO-GC's by fusion of the α amino-terminus to the β₁ carboxy-terminus leading to a monomeric enzyme complex. Surprisingly but in accordance with the FRET results these conjoined NO-GC's (β₁α₁, β₁α₂) showed specific enzyme activity and stimulation by NO and various modulators of GC activity.

## Conclusion

These obligate enzyme variants faithfully reproduced the pharmacological properties of the heterodimeric enzymes including an isoform specific differential activation of the NO-independent drug cinaciguat. Novel applications of conjoined NO-GC's including adenoviral gene transfer will be discussed.

Published: 1 August 2011

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<footnote>* Correspondence: s Behrends@tu-bs.de
Institut für Pharmakologie, Toxikologie und Klinische Pharmazie, TU
Braunschweig, Germany</footnote>

<footnote>doi:10.1186/1471-2210-11-S1-P6

Cite this article as: Behrends et al.: Conjoined NO-sensitive guanylyl cyclases. BMC Pharmacology 2011 11(Suppl 1):P6.</footnote>