Implications of threonine hydrogen bonding in the glycophorin A transmembrane helix dimer.
Implications of threonine hydrogen bonding in the glycophorin A transmembrane helix dimer.
复制标题
血型糖蛋白 A 跨膜螺旋二聚体中苏氨酸氢键的影响。
DOI：
10.1016/s0006-3495(02)75590-2
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发表时间：
2002
影响因子：
3.4
通讯作者：
Aimoto,Saburo
中科院分区：
文献类型：
--
作者：
Smith,StevenO;Eilers,Markus;Song,David;Crocker,Evan;Ying,Weiwen;Groesbeek,Michel;Metz,Guenter;Ziliox,Martine;Aimoto,Saburo
血糖素A的跨膜螺旋包含一个七个残基的基序LIxxGVxxGVxxT，它介导蛋白质的二聚化。苏氨酸是该基序中唯一具有通过氢键作用稳定二聚体的极性氨基酸。利用偏振傅里叶变换红外光谱建立了一种将血糖素A跨膜肽结合到膜双层中的可靠方案。对1655 cm的−1酰胺I振动的二色性比的分析表明，洗涤剂透析重组的多肽具有跨膜取向，螺旋交叉角为35°。固体核磁共振波谱被用来建立Thr-87在二聚体界面上的构象和堆积的高分辨率结构约束。旋转共振测量结果表明，Thr-87的γ-甲基和主链羰基之间的距离为2.9？，与−构象的χ1扭转角是一致的。旋转回波双共振测量表明，Thr-87的γ-甲基与ILE-88的主链氮在二聚体界面上紧密堆积。短的螺旋间距将Thr-87的β-羟基置于Val-84的相对螺旋上的主链羰基的氢键范围内。这些结果细化了膜双层中的血糖蛋白A二聚体的结构，并突出了小残基和极性残基在膜蛋白跨膜螺旋紧密结合中的互补作用。
The transmembrane helix of glycophorin A contains a seven-residue motif, LIxxGVxxGVxxT, that mediates protein dimerization. Threonine is the only polar amino acid in this motif with the potential to stabilize the dimer through hydrogen-bonding interactions. Polarized Fourier transform infrared spectroscopy is used to establish a robust protocol for incorporating glycophorin A transmembrane peptides into membrane bilayers. Analysis of the dichroic ratio of the 1655-cm−1amide I vibration indicates that peptides reconstituted by detergent dialysis have a transmembrane orientation with a helix crossing angle of <35°. Solid-state nuclear magnetic resonance spectroscopy is used to establish high resolution structural restraints on the conformation and packing of Thr-87 in the dimer interface. Rotational resonance measurement of a 2.9-Å distance between theγ-methyl and backbone carbonyl carbons of Thr-87 is consistent with agauche− conformation for theχ1 torsion angle. Rotational-echo double-resonance measurements demonstrate close packing (4.0±0.2Å) of the Thr-87γ-methyl group with the backbone nitrogen of Ile-88 across the dimer interface. The short interhelical distance places theβ-hydroxyl of Thr-87 within hydrogen-bonding range of the backbone carbonyl of Val-84 on the opposing helix. These results refine the structure of the glycophorin A dimer in membrane bilayers and highlight the complementary role of small and polar residues in the tight association of transmembrane helices in membrane proteins.