The α-helical propensity of the cytoplasmic domain of phospholamban:: A molecular dynamics simulation of the effect of phosphorylation and mutation
The α-helical propensity of the cytoplasmic domain of phospholamban:: A molecular dynamics simulation of the effect of phosphorylation and mutation
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DOI：
10.1529/biophysj.104.054460
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发表时间：
2005-05-01
影响因子：
3.4
通讯作者：
Thomas, DD
中科院分区：
文献类型：
--
作者：
Paterlini, MG;Thomas, DD
我们已经使用分子动力学模拟来研究磷酸化和突变对受磷蛋白（PLB）的胞质结构域的影响，受磷蛋白是一种52个残基的蛋白质，调节心肌中的钙泵。在300 K下在显式水系统中对跨越PLB的前25个残基的三种肽进行模拟：野生型（PLB 1 -25）、在Ser 16处磷酸化的PLB 1 -25和具有已知引起人类心脏病的R9 C突变的PLB 1 -25。未磷酸化的肽在整个26-ns的模拟中保持从3到15的螺旋构象，与光谱数据一致。与模拟的第四个肽截短在Pro21的比较表明，该地区的重要性，从17日至21日在防止当地展开的螺旋。结果表明，残基11-16更有可能展开时，特定的加帽基序不存在。有人提出，蛋白激酶A利用11-21区域的内在灵活性时，结合PLB。与可用的CD和NMR数据一致，模拟显示磷酸化后螺旋含量减少。磷酸化肽的特征在于跨越残基3-11的螺旋，随后是优化磷酸化Ser-16和Arg-13的侧链之间的盐桥相互作用的转角。用Cys替换Arg-9导致螺旋从C9展开，并且螺旋构象总体降低。模拟结果表明，展开的开始是由于增加溶剂的可及性附近的较小的Cys的骨架原子。有人提出，在Ser-16磷酸化或R9 C突变的PLB的抑制效力的损失是由于一个类似的机制，其中部分解折叠的PLB的胞质螺旋的结果在一个构象，与钙泵的胞质结构域相互作用，以减轻其抑制。
We have used molecular dynamics simulations to investigate the effect of phosphorylation and mutation on the cytoplasmic domain of phospholamban (PLB), a 52-residue protein that regulates the calcium pump in cardiac muscle. Simulations were carried out in explicit water systems at 300 K for three peptides spanning the first 25 residues of PLB: wildtype (PLB1-25), PLB1-25 phosphorylated at Ser16 and PLB1-25 with the R9C mutation, which is known to cause human heart disease. The unphosphorylated peptide maintains a helical conformation from 3 to 15 throughout a 26-ns simulation, in agreement with spectroscopic data. Comparison with simulations of a fourth peptide truncated at Pro21 showed the importance of the region from 17 to 21 in preventing local unfolding of the helix. The results suggest that residues 11-16 are more likely to unfold when specific capping motifs are not present. It is proposed that protein kinase A exploits the intrinsic flexibility of the 11-21 region when binding PLB. In agreement with available CD and NMR data, the simulations show a decrease in the helical content upon phosphorylation. The phosphorylated peptide is characterized by helix spanning residues 3-11, followed by a turn that optimizes the salt-bridge interaction between the side chains of the phosphorylated Ser-16 and Arg-13. Replacing Arg-9 with Cys results in unfolding of the helix from C9 and an overall decrease of the helical conformation. The simulations show that initiation of unfolding is due to increased solvent accessibility of the backbone atoms near the smaller Cys. It is proposed that the loss of inhibitory potency upon Ser-16 phosphorylation or R9C mutation of PLB is due to a similar mechanism, in which the partial unfolding of the cytoplasmic helix of PLB results in a conformation that interacts with the cytoplasmic domain of the calcium pump to relieve its inhibition.