Solution structure of calcium-bound rat S100B(ββ) as determined by nuclear magnetic resonance spectroscopy
Solution structure of calcium-bound rat S100B(ββ) as determined by nuclear magnetic resonance spectroscopy
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DOI：
10.1021/bi972635p
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发表时间：
1998-03-03
期刊：
影响因子：
2.9
通讯作者：
Weber, DJ
中科院分区：
文献类型：
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作者：
Drohat, AC;Baldisseri, DM;Weber, DJ
利用一系列二维(2D)、三维(3D)和四维(4D)核磁共振实验数据确定了钙结合大鼠S100B(Beta)的三维结构。每个S100β亚基(91个残基)包含4个螺旋(螺旋1，E2-R20；螺旋2，K29-N38；螺旋3，Q50-D61；螺旋4，F70-A83)和一个反平行的β-折叠(链I，K26-K28；链2，E67-D69)，它将正常和假性EF-手连接在一起。如先前发现的大鼠apo-S100B(Beta Beta)[Drohat，A.C.，et al.(1996年)生物化学35,11577-11588]，螺旋1、1‘、4和4’在对称二聚体界面形成X型四螺旋集束。此外，钙离子结合并不显著改变假EF-手中螺旋1和2的螺旋角(APE，Omega(1-2)=132+/-4度；和钙结合，Omega(1-2)=137+/-5度)。然而，正常EF手中3和4螺旋的螺旋角(Omega(3-4)=106+/-4度)随着钙离子的加入(Delta Omega(3-4)=112+/-5度)发生了显著变化，与钙结合蛋白D-9K、钙调素和肌钙蛋白(小于或等于Omega小于或等于128度)的EF手中的螺旋间角相似。此外，正如在钙结合蛋白D-9K中观察到的那样，每个S100β亚基内的四个螺旋形成一个扩张型四螺旋束(四个垂直螺旋)。涉及螺旋3的大型钙依赖构象变化暴露了一个裂隙，由铰链区、C-末端环和螺旋3中的残基定义，而后者在载脂蛋白结构中缺失。钙离子结合的S100B(β-β)上的这个表面对于靶蛋白结合可能是重要的。
The three-dimensional structure of Ca2+-bound rat S100B(beta beta) has been determined using data from a series of two-dimensional (2D), three-dimensional (3D), and four-dimensional (4D) nuclear magnetic resonance (NMR) experiments. Each S100 beta subunit (91 residues) contains four helixes (helix 1, E2-R20; helix 2, K29-N38; helix 3, Q50-D61; and helix 4, F70-A83) and one antiparallel beta-sheet (strand I, K26-K28; and strand 2, E67-D69) which brings the normal and pseudo EF-hands together. As found previously for rat apo-S100B(beta beta) [Drohat, A. C., et al. (1996) Biochemistry 35, 11577-11588], helixes 1, 1', 4, and 4' associate to form an X-type four-helix bundle at the symmetric dimer interface. Additionally, Ca2+ binding does not significantly change the interhelical angle of helixes 1 and 2 in the pseudo EF-hand (ape, Omega(1-2) = 132 +/- 4 degrees; and Ca2+-bound, Omega(1-2) = 137 +/- 5 degrees). However, the interhelical angle of helixes 3 and 4 in the normal EF-hand (Omega(3-4) = 106 +/- 4 degrees) changed significantly upon the addition of Ca2+ (Delta Omega(3-4) = 112 +/- 5 degrees) and is similar to that of the Ca2+-bound EF-hands in calbindin D-9K, calmodulin, and troponin (84 degrees less than or equal to Omega less than or equal to 128 degrees). Further, the four helixes within each S100 beta subunit form a splayed-type four-helix bundle (four perpendicular helixes) as observed in Ca2+-bound calbindin D-9K The large Ca2+-dependent conformational change involving helix 3 exposes a cleft, defined by residues in the hinge region, the C-terminal loop, and helix 3, which is absent in the apo structure. This surface on Ca2+-bound S100B(beta beta) is likely important for target protein binding.