Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, Minneapolis, MN 55455, USA.
Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
Structure. 2022 Mar 3;30(3):360-370.e6. doi: 10.1016/j.str.2021.11.003. Epub 2021 Dec 6.
SERCA is a P-type ATPase embedded in the sarcoplasmic reticulum and plays a central role in muscle relaxation. SERCA's function is regulated by single-pass membrane proteins called regulins. Unlike other regulins, dwarf open reading frame (DWORF) expressed in cardiac muscle has a unique activating effect. Here, we determine the structure and topology of DWORF in lipid bilayers using a combination of oriented sample solid-state NMR spectroscopy and replica-averaged orientationally restrained molecular dynamics. We found that DWORF's structural topology consists of a dynamic N-terminal domain, an amphipathic juxtamembrane helix that crosses the lipid groups at an angle of 64°, and a transmembrane C-terminal helix with an angle of 32°. A kink induced by Pro15, unique to DWORF, separates the two helical domains. A single Pro15Ala mutant significantly decreases the kink and eliminates DWORF's activating effect on SERCA. Overall, our findings directly link DWORF's structural topology to its activating effect on SERCA.
肌浆网 Ca2+-ATP 酶（SERCA）是一种镶嵌于肌浆网的 P 型 ATP 酶，在肌肉松弛中起着核心作用。SERCA 的功能受称为调节蛋白的单次跨膜蛋白调节。与其他调节蛋白不同，心肌中表达的矮小开放阅读框（DWORF）具有独特的激活作用。在这里，我们使用定向样品固态 NMR 光谱和复制品平均取向约束分子动力学相结合的方法，在脂质双层中确定了 DWORF 的结构和拓扑。我们发现，DWORF 的结构拓扑由一个动态的 N 端结构域、一个跨膜 C 端螺旋和一个跨膜 C 端螺旋组成，该螺旋以 64°的角度穿过脂质基团，具有独特的激活作用。由 Pro15 引起的扭曲，是 DWORF 所特有的，将两个螺旋结构域分开。单个 Pro15Ala 突变显著减小了扭曲程度，并消除了 DWORF 对 SERCA 的激活作用。总的来说，我们的发现直接将 DWORF 的结构拓扑与其对 SERCA 的激活作用联系起来。
