ジャーナル: J Biol Chem / 年: 2014 タイトル: Architecture of the nitric-oxide synthase holoenzyme reveals large conformational changes and a calmodulin-driven release of the FMN domain. 著者: Adam L Yokom / Yoshihiro Morishima / Miranda Lau / Min Su / Alisa Glukhova / Yoichi Osawa / Daniel R Southworth / 要旨: Nitric-oxide synthase (NOS) is required in mammals to generate NO for regulating blood pressure, synaptic response, and immune defense. NOS is a large homodimer with well characterized reductase and ...Nitric-oxide synthase (NOS) is required in mammals to generate NO for regulating blood pressure, synaptic response, and immune defense. NOS is a large homodimer with well characterized reductase and oxygenase domains that coordinate a multistep, interdomain electron transfer mechanism to oxidize l-arginine and generate NO. Ca(2+)-calmodulin (CaM) binds between the reductase and oxygenase domains to activate NO synthesis. Although NOS has long been proposed to adopt distinct conformations that alternate between interflavin and FMN-heme electron transfer steps, structures of the holoenzyme have remained elusive and the CaM-bound arrangement is unknown. Here we have applied single particle electron microscopy (EM) methods to characterize the full-length of the neuronal isoform (nNOS) complex and determine the structural mechanism of CaM activation. We have identified that nNOS adopts an ensemble of open and closed conformational states and that CaM binding induces a dramatic rearrangement of the reductase domain. Our three-dimensional reconstruction of the intact nNOS-CaM complex reveals a closed conformation and a cross-monomer arrangement with the FMN domain rotated away from the NADPH-FAD center, toward the oxygenase dimer. This work captures, for the first time, the reductase-oxygenase structural arrangement and the CaM-dependent release of the FMN domain that coordinates to drive electron transfer across the domains during catalysis.
全体 : Rat neuronal nitric oxide synthase dimer bound to calmodulin
全体
名称: Rat neuronal nitric oxide synthase dimer bound to calmodulin
要素
試料: Rat neuronal nitric oxide synthase dimer bound to calmodulin
タンパク質・ペプチド: neuronal nitric oxide synthase
タンパク質・ペプチド: calmodulin
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超分子 #1000: Rat neuronal nitric oxide synthase dimer bound to calmodulin
超分子
名称: Rat neuronal nitric oxide synthase dimer bound to calmodulin タイプ: sample / ID: 1000 詳細: The sample was crosslinked with 0.01% glutaraldehyde prior to imaging using negative staining. 集合状態: Homodimer of nNOS bound to two CaM proteins / Number unique components: 2