Crystal structure of an oxygen-binding heme domain related to soluble guanylate cyclases

Proc Natl Acad Sci U S A. 2004 Aug 31;101(35):12854-9. doi: 10.1073/pnas.0405188101. Epub 2004 Aug 23.


Soluble guanylate cyclases are nitric oxide-responsive signaling proteins in which the nitric oxide sensor is a heme-binding domain of unknown structure that we have termed the heme-NO and oxygen binding (H-NOX) domain. H-NOX domains are also found in bacteria, either as isolated domains, or are fused through a membrane-spanning region to methyl-accepting chemotaxis proteins. We have determined the crystal structure of an oxygen-binding H-NOX domain of one such signaling protein from the obligate anaerobe Thermoanaerobacter tengcongensis at 1.77-angstroms resolution, revealing a protein fold unrelated to known structures. Particularly striking is the structure of the protoporphyrin IX group, which is distorted from planarity to an extent not seen before in protein-bound heme groups. Comparison of the structure of the H-NOX domain in two different crystal forms suggests a mechanism whereby alteration in the degree of distortion of the heme group is coupled to changes on the molecular surface of the H-NOX domain and potentially to changes in intermolecular interactions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Chemotaxis / physiology
  • Guanylate Cyclase / chemistry*
  • Guanylate Cyclase / metabolism
  • Heme / metabolism*
  • Molecular Sequence Data
  • Oxygen / metabolism*
  • Protein Structure, Tertiary


  • Heme
  • Guanylate Cyclase
  • Oxygen

Associated data

  • PDB/1U4H
  • PDB/1U55
  • PDB/1U56