Allosteric activation of the nitric oxide receptor soluble guanylate cyclase mapped by cryo-electron microscopy

Abstract

Soluble guanylate cyclase (sGC) is the primary receptor for nitric oxide (NO) in mammalian nitric oxide signaling. We determined structures of full-length Manduca sexta sGC in both inactive and active states using cryo-electron microscopy. NO and the sGC-specific stimulator YC-1 induce a 71° rotation of the heme-binding β H-NOX and PAS domains. Repositioning of the β H-NOX domain leads to a straightening of the coiled-coil domains, which, in turn, use the motion to move the catalytic domains into an active conformation. YC-1 binds directly between the β H-NOX domain and the two CC domains. The structural elongation of the particle observed in cryo-EM was corroborated in solution using small angle X-ray scattering (SAXS). These structures delineate the endpoints of the allosteric transition responsible for the major cyclic GMP-dependent physiological effects of NO.

Solution structures of the Shewanella woodyiH‐NOX protein in the presence and absence of soluble guanylyl cyclase stimulator IWP‐051

“…Dynamics in these regions increase on binding IWP‐051, as do dynamics in the binding site (Figure 6). Interestingly, residues 38 and 40 directly contact the sGC coiled coil in the activated conformation observed by cryo‐EM (Figure 7), but not in the inactive form 16,17 …”

“…Comparison of stimulator binding sites. Shown is the cryo‐EM model for activated Manduca sGC (PDB 6PAT) 17 as a ribbon drawing with α chain in green, β chain in cyan and heme in stick format. Residues contacting Sw H‐NOX are indicated in marine blue (L12, D15, E16, L69, K72, and K73).…”

“…PCC 7120 ( Ns H‐NOX), Shewanella oneidensis ( So H‐NOX ), Shewanella woodyi ( Sw H‐NOX ), and Cb SONO . More recently, moderate resolution (3.8–5.8 Å) cryo‐electron microscopy models for sGC in inactive and active conformations show sGC undergoing a dramatic change in conformation upon activation that involves kink‐straightening and repacking of the coiled‐coil domain, 16,17 which has conserved positions of instability to facilitate activation 18 . The H‐NOX domain lies along the coiled coil domain in these structures, and density for YC‐1 can be seen at the interface of the H‐NOX and coiled‐coil domains 17 …”

Nitric oxide (NO) signaling inTrichoplaxand related species: Microchemical characterization and the lineage-specific diversification

“…NO can act via cyclic guanosine monophosphate or cGMP as second messenger. In this signaling pathway, NO binds to the heme group of soluble guanylate cyclases (sGCs), member of the adenylyl cyclase superfamily 79,80 , with a characteristic catalytic CYC domain, leading to the increase of cGMP synthesis [6][7][8][81][82][83][84][85] ; by binding to ATP, sGC can also couple NO signaling to cellular metabolism 86 .…”

Wedging open a catalytic site

“…Two questions have been the subject of intense scrutiny and conflicting data: where does YC-1 bind to sGC, and how does it increase the impact of NO. Now, in eLife, Michael Marletta, Jim Hurley and colleagues at Berkeley, including Ben Horst and Adam Yokom as joint first authors, report the results of cryo-electron microscopy (cryo-EM) and small angle X-ray scattering experiments that shed light on these questions (Horst et al, 2019).…”