Abstract
We recently showed that inducible nitric oxide synthase conformational intermediates can be resolved via FMN fluorescence lifetimes. Here we show that neuronal NOS activation by calmodulin removes constraints favoring a closed 'input state', increasing occupation of other states and facilitating conformational transitions. The 90 ps FMN input state lifetime distinguishes it from ∼4 ns 'open' states in which FMN does not interact strongly with other groups, or 0.9 ns output states in which FMN interacts with ferriheme. Enablement of the conformational cycle is an important paradigm for control in nNOS and related enzymes, and may extend to other control modalities.
Copyright © 2012. Published by Elsevier B.V.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Algorithms
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Binding Sites
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Calmodulin / chemistry
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Calmodulin / metabolism*
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Enzyme Activation
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Flavin Mononucleotide / metabolism
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Hemin / metabolism
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Holoenzymes / chemistry
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Holoenzymes / genetics
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Holoenzymes / metabolism
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Humans
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Kinetics
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Mutant Proteins / chemistry
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Mutant Proteins / metabolism
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Nitric Oxide Synthase Type I / chemistry
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Nitric Oxide Synthase Type I / genetics
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Nitric Oxide Synthase Type I / metabolism*
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Protein Conformation
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Protein Interaction Domains and Motifs
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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Spectrometry, Fluorescence
Substances
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Calmodulin
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Holoenzymes
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Mutant Proteins
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Recombinant Proteins
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Hemin
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Flavin Mononucleotide
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NOS1 protein, human
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Nitric Oxide Synthase Type I