National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)
R01HL036153
米国
引用
ジャーナル: J Gen Physiol / 年: 2023 タイトル: Myosin loop-4 is critical for optimal tropomyosin repositioning on actin during muscle activation and relaxation. 著者: Matthew H Doran / Michael J Rynkiewicz / Elumalai Pavadai / Skylar M L Bodt / David Rasicci / Jeffrey R Moore / Christopher M Yengo / Esther Bullitt / William Lehman / 要旨: During force-generating steps of the muscle crossbridge cycle, the tip of the myosin motor, specifically loop-4, contacts the tropomyosin cable of actin filaments. In the current study, we determined ...During force-generating steps of the muscle crossbridge cycle, the tip of the myosin motor, specifically loop-4, contacts the tropomyosin cable of actin filaments. In the current study, we determined the corresponding effect of myosin loop-4 on the regulatory positioning of tropomyosin on actin. To accomplish this, we compared high-resolution cryo-EM structures of myosin S1-decorated thin filaments containing either wild-type or a loop-4 mutant construct, where the seven-residue portion of myosin loop-4 that contacts tropomyosin was replaced by glycine residues, thus removing polar side chains from residues 366-372. Cryo-EM analysis of fully decorated actin-tropomyosin filaments with wild-type and mutant S1, yielded 3.4-3.6 Å resolution reconstructions, with even higher definition at the actin-myosin interface. Loop-4 densities both in wild-type and mutant S1 were clearly identified, and side chains were resolved in the wild-type structure. Aside from loop-4, actin and myosin structural domains were indistinguishable from each other when filaments were decorated with either mutant or wild-type S1. In marked contrast, the position of tropomyosin on actin in the two reconstructions differed by 3 to 4 Å. In maps of filaments containing the mutant, tropomyosin was located closer to the myosin-head and thus moved in the direction of the C-state conformation adopted by myosin-free thin filaments. Complementary interaction energy measurements showed that tropomyosin in the mutant thin filaments sits on actin in a local energy minimum, whereas tropomyosin is positioned by wild-type S1 in an energetically unfavorable location. We propose that the high potential energy associated with tropomyosin positioning in wild-type filaments favors an effective transition to B- and C-states following release of myosin from the thin filaments during relaxation.
全体 : Human cardiac actin-tropomyosin-beta-myosin II complex with 7G lo...
全体
名称: Human cardiac actin-tropomyosin-beta-myosin II complex with 7G loop 4 mutation
要素
複合体: Human cardiac actin-tropomyosin-beta-myosin II complex with 7G loop 4 mutation
複合体: Cardiac F-actin complex
タンパク質・ペプチド: Actin, alpha cardiac muscle 1
複合体: Human beta-cardiac myosin II with seven (366-372) loop 4 residues mutated to glycine.
タンパク質・ペプチド: Myosin-7
複合体: Human cardiac tropomyosin
タンパク質・ペプチド: Tropomyosin alpha-1 chain
リガンド: ADENOSINE-5'-DIPHOSPHATE
リガンド: MAGNESIUM ION
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超分子 #1: Human cardiac actin-tropomyosin-beta-myosin II complex with 7G lo...
超分子
名称: Human cardiac actin-tropomyosin-beta-myosin II complex with 7G loop 4 mutation タイプ: complex / ID: 1 / 親要素: 0 / 含まれる分子: #1-#3 詳細: Cardiac actomyosin-tropomyosin complex with seven loop 4 residues mutated to glycine.
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超分子 #2: Cardiac F-actin complex
超分子
名称: Cardiac F-actin complex / タイプ: complex / ID: 2 / 親要素: 1 / 含まれる分子: #2 / 詳細: F-actin forms the backbone of the complex
由来(天然)
生物種: Sus scrofa (ブタ)
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超分子 #3: Human beta-cardiac myosin II with seven (366-372) loop 4 residues...
超分子
名称: Human beta-cardiac myosin II with seven (366-372) loop 4 residues mutated to glycine. タイプ: complex / ID: 3 / 親要素: 1 / 含まれる分子: #1 詳細: The motor domain of the myosin saturates the actin filament.
由来(天然)
生物種: Homo sapiens (ヒト)
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超分子 #4: Human cardiac tropomyosin
超分子
名称: Human cardiac tropomyosin / タイプ: complex / ID: 4 / 親要素: 1 / 含まれる分子: #3 / 詳細: Tropomyosin wraps around the F-actin core.