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. Author manuscript; available in PMC: 2012 Nov 1.
Published in final edited form as: FEBS J. 2011 Sep 15;278(21):4055–4069. doi: 10.1111/j.1742-4658.2011.08310.x

Fig 1. Three-state model of NOS FMN domain function in electron transfer and heme reduction.

Fig 1

The FMN domain is attached in NOS by two hinge elements (H1 & H2). Equilibrium A defines a shielded (closed) conformation which has the FMN and FNR domains interacting (left) and a deshielded (open) non-interacting conformation (center) that allows the FMN domain to interact with electron acceptors such as cytochrome c. Equilibrium B defines the FMN–NOSoxy domain interaction required for heme reduction and NO synthesis. Complementary electrostatic interactions (blue, red) are thought to aid both FMN domain interactions in NOS.