¹H, ¹³C, and ¹⁵N backbone and side-chain resonance assignments of the Nostoc sp. H-NOX C139A variant in complex with the soluble Guanylyl Cyclase inhibitor Zinc Protoporphyrin IX.

The H-NOX (Heme-Nitric oxide/Oxygen binding) domain is highly conserved among both eukaryotes and bacteria. In human soluble Guanylyl Cyclase (sGC), the H-NOX domain functions as a sensor for the gaseous signaling molecule Nitric Oxide (NO). Located at the N-terminus of the enzyme, the heme B-binding H-NOX domain regulates the catalytic domain at the C-terminus, which catalyzes the conversion of GTP (guanosine 5'-triphosphate) to cGMP (cyclic Guanosine MonoPhosphate). The present study employs the bacterial homolog Nostoc sp. H-NOX (Ns H-NOX) C139A mutant together with the sGC inhibitor Zinc Protoporphyrin IX (ZnPPIX) as experimental tools to investigate the still poorly understood mechanisms underlying sGC activation and inhibition, and to elucidate either the chemical features of novel scaffolds associated with a new class of activators, or the distinct activities imposed by two prosthetic groups sharing the same organic framework, but differing in the chelated transition metal. Here, we present the conditions employed for the formation of the complex between the Ns H-NOX C139A mutant and the sGC inhibitor ZnPPIX, together with the UV-Vis absorption spectra of the heme-bound and ZnPPIX-bound protein forms. Furthermore, we report the NMR backbone and side-chain resonance assignments (¹H, ¹³C, ¹⁵N) of the complex, as well as the chemical shift-based secondary structure predictions. These data will be used for comparative analysis of ¹⁵N NMR relaxation experiments in the basal, fully active and inactive H-NOX states, aiming to elucidate the role of Η-ΝΟΧ protein dynamics in the initiation and propagation of sGC activation signal.

© 2026. The Author(s).