Influence of interfacial tryptophan residues on an arginine-flanked transmembrane helix
Influence of interfacial tryptophan residues on an arginine-flanked transmembrane helix
复制标题
界面色氨酸残基对精氨酸侧翼跨膜螺旋的影响
DOI：
10.1016/j.bbamem.2019.183134
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Koeppe, Roger E.
中科院分区：
文献类型：
--
作者：
Sustich, Sara J.;Afrose, Fahmida;Greathouse, Denise V.;Koeppe, Roger E.
膜蛋白的跨膜螺旋通常两侧是界面带电或芳香族残基，这些残基可能有助于锚定跨膜蛋白。对于分离的单跨度螺旋，界面残基对于稳定特定倾斜的跨膜方向可能特别重要。肽 RWALP23（乙酰基-GR2ALW(LA)6LWLAR22A-酰胺）已用于研究界面精氨酸和色氨酸之间的相互作用。在这里，我们用 A5 和 A19 替换 RWALP23 的色氨酸，以研究单独的精氨酸在不同脂质双层中的螺旋磨损和方向。掺入中心序列的氘代丙氨酸允许通过 DOPC、DMPC 和 DLPC 双层中的固态 2 H NMR 来评估核心螺旋的方向和稳定性。当 R2 和 R22 存在时，发现与双层正常的螺旋倾斜度略有增加，并且当色氨酸 W5 和 W19 被丙氨酸取代时进一步增加。在所有情况下，螺旋动态平均的程度仍然很低。对于这里考虑的每个脂质膜中的所有螺旋，优选的螺旋方位角旋转基本上是恒定的。位于肽核心区域之外的丙氨酸对螺旋完整性敏感。因此，新的丙氨酸 A5 和 A19 提供了有关核心螺旋长度和末端解开开始的新信息。残基 A19 基本上保留在每个脂质膜的中心螺旋上，而残基 A3、A5 和 A21 偏离核心螺旋的程度取决于膜的厚度。因此，两端的差异分解以暴露肽主链基团进行氢键结合，与特定的界面侧链一起作用以稳定跨膜螺旋。
The transmembrane helices of membrane proteins often are flanked by interfacial charged or aromatic residues that potentially help to anchor the membrane-spanning protein. For isolated single-span helices, the interfacial residues may be especially important for stabilizing particular tilted transmembrane orientations. The peptide RWALP23 (acetyl-GR2ALW(LA)6LWLAR22A-amide) has been employed to investigate the interplay between interfacial arginines and tryptophans. Here we replace the tryptophans of RWALP23 with A5 and A19, to investigate arginines alone with respect to helix fraying and orientation in varying lipid bilayers. Deuterated alanines incorporated into the central sequence allow the orientation and stability of the core helix to be assessed by means of solid -state2H NMR in bilayers of DOPC, DMPC and DLPC. The helix tilt from the bilayer normal is found to increase slightly when R2 and R22 are present, and increases still further when the tryptophans W5 and W19 are replaced by alanines. The extent of helix dynamic averaging remains low in all cases. The preferred helix azimuthal rotation is essentially constant for all of the helices in each of the lipid membranes considered here. The alanines located outside of the core region of the peptide are sensitive to helical integrity. The new alanines, A5 and A19, therefore, provide new information about the length of the core helix and the onset of unraveling of the terminals. Residue A19 remains essentially on the central helix in each lipid membrane, while residues A3, A5 and A21 deviate from the core helix to an extent that depends on the membrane thickness. Differential unraveling of the two ends to expose peptide backbone groups for hydrogen bonding therefore acts together with specific interfacial side chains to stabilize a transmembrane helix.