Nitric Oxide Synthase: Difference between revisions

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Heme is a [http://en.wikipedia.org/wiki/Prosthetic_group prosthetic group] containing an iron atom in the center of a large organic ring called [http://en.wikipedia.org/wiki/Porphyrin porphyrin](See picture). The heme group can have several functions: it can act as a transporter of diatomic gases, as a chemical catalyst, detect diatomic gases, and take part in electron transfer. In NOS the heme both binds a diatomic molecule (CO, NO, O<sub>2</sub>) and functions in the multi electron pathway <ref>PMID: 16804678</ref>.  
Heme is a [http://en.wikipedia.org/wiki/Prosthetic_group prosthetic group] containing an iron atom in the center of a large organic ring called [http://en.wikipedia.org/wiki/Porphyrin porphyrin](See picture). The heme group can have several functions: it can act as a transporter of diatomic gases, as a chemical catalyst, detect diatomic gases, and take part in electron transfer. In NOS the heme both binds a diatomic molecule (CO, NO, O<sub>2</sub>) and functions in the multi electron pathway <ref>PMID: 16804678</ref>.  


As mentioned, the heme group takes part in the creation of the cavity running through the monomer. Arginine/Citrulline diffuses in and out this cavity. In closed conformation, the cavity is so small that only a water molecule can enter. The heme group in the cavity is held in place by van der Waals interactions with hydrophobic and aliphatic side chains of the protein making up the cavity. The heme has its propionate groups facing the interface. The propionic acid groups of heme forms several hydrogen bonds with water molecules inside the cavity. One of these groups hydrogenbonds to H<sub>4</sub>B. The iron in heme in pentacoordinated <ref>PMID: 10074942</ref>, with its axial ligand supplied by a specific Cys S atom.
As mentioned, the heme group takes part in the creation of the cavity running through the monomer. Arginine/Citrulline diffuses in and out this cavity. In closed conformation, the cavity is so small that only a water molecule can enter. The heme group in the cavity is held in place by van der Waals interactions with hydrophobic and aliphatic side chains of the protein making up the cavity. The heme has its [http://en.wikipedia.org/wiki/Propionate propionate group] facing the interface. The propionic acid groups of heme forms several hydrogen bonds with water molecules inside the cavity. One of these groups hydrogenbonds to H<sub>4</sub>B. The iron in heme in pentacoordinated <ref>PMID: 10074942</ref>, with its axial ligand supplied by a specific Cys S atom.




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