ジャーナル: Nat Struct Mol Biol / 年: 2023 タイトル: Molecular mechanisms of inorganic-phosphate release from the core and barbed end of actin filaments. 著者: Wout Oosterheert / Florian E C Blanc / Ankit Roy / Alexander Belyy / Micaela Boiero Sanders / Oliver Hofnagel / Gerhard Hummer / Peter Bieling / Stefan Raunser / 要旨: The release of inorganic phosphate (P) from actin filaments constitutes a key step in their regulated turnover, which is fundamental to many cellular functions. The mechanisms underlying P release ...The release of inorganic phosphate (P) from actin filaments constitutes a key step in their regulated turnover, which is fundamental to many cellular functions. The mechanisms underlying P release from the core and barbed end of actin filaments remain unclear. Here, using human and bovine actin isoforms, we combine cryo-EM with molecular-dynamics simulations and in vitro reconstitution to demonstrate how actin releases P through a 'molecular backdoor'. While constantly open at the barbed end, the backdoor is predominantly closed in filament-core subunits and opens only transiently through concerted amino acid rearrangements. This explains why P escapes rapidly from the filament end but slowly from internal subunits. In a nemaline-myopathy-associated actin variant, the backdoor is predominantly open in filament-core subunits, resulting in accelerated P release and filaments with drastically shortened ADP-P caps. Our results provide the molecular basis for P release from actin and exemplify how a disease-linked mutation distorts the nucleotide-state distribution and atomic structure of the filament.
名称: actin-phalloidin complex / タイプ: complex / ID: 1 / 親要素: 0 / 含まれる分子: #1 詳細: Actin was purified as monomer from bovine thymus. Short filaments were reconstituted in vitro to obtain the barbed end structure.
想定した対称性 - 点群: C1 (非対称) / 解像度のタイプ: BY AUTHOR / 解像度: 3.59 Å / 解像度の算出法: FSC 0.143 CUT-OFF / ソフトウェア - 名称: cryoSPARC (ver. 3.3.2) 詳細: Performed in CryoSPARC. All barbed end particles were isolated from from other particles that represented pointed end and filament core. 使用した粒子像数: 43618
初期 角度割当
タイプ: MAXIMUM LIKELIHOOD / ソフトウェア - 名称: cryoSPARC (ver. 3.3.2) / 詳細: First refinement performed in CryoSPARC.
最終 角度割当
タイプ: MAXIMUM LIKELIHOOD / ソフトウェア - 名称: cryoSPARC (ver. 3.3.2) 詳細: Final refinement performed in CryoSPARC. The barbed end structure was refined as a single particle without applying any restraints.