Sensitive and selective detection of nitric oxide using an H-NOX domain.

Tt Y140F, a mutant of the H-NOX (Heme-Nitric Oxide or OXygen binding domain) protein from Thermoanaerobacter tengcongensis, is presented as a novel genetically encoded NO sensor. Tt Y140F is easily purified and obtained in high yields from standard E. coli expression systems. It is extremely stable as both the ferrous unligated and ferrous-nitrosyl complexes in air over a range of temperatures (up to 70 degrees C) without oxidizing, denaturing, or binding O2. NO binding is quantitative and can be followed using simple absorbance spectroscopy. In theory, NO concentrations between 300 nM and 30 muM can be accurately and easily detected.