Conformation of the antifreeze glycoprotein of polar fish.
Conformation of the antifreeze glycoprotein of polar fish.
复制标题
极地鱼抗冻糖蛋白的构象。
DOI：
10.1016/0003-9861(84)90582-4
复制
发表时间：
1984
影响因子：
3.9
通讯作者：
Feeney,RE
中科院分区：
文献类型：
--
作者：
Bush,CA;Ralapati,S;Matson,GM;Yamasaki,RB;Osuga,DT;Yeh,Y;Feeney,RE
高场质子和13 C NMR光谱已被用来测试和完善最近的建议，基于真空紫外圆二色性结果，一个三重左手螺旋构象的抗冻糖蛋白（AFGP）。通过与模型化合物的光谱比较，通过选择性解耦，以及通过测量核Overhauser效应（nOe），已经对糖三肽重复单元的质子进行了部分分配。在40 °C下，AFGP级分8（Mr 2600）显示出在较低温度下加宽的2 Hz线宽。无论是1H或13 C化学位移强烈依赖于温度，表明没有突然的构象转变。丙氨酸α和β质子之间的nOe随温度和场强而变化，从50 °C和80 MHz的小的正增强到3 °C和300 MHz的大的负效应，表明旋转相关时间随温度的实质性变化。较高分子量级分1-4在所有温度下均显示负nOe。级分1-4的CD光谱在3 ° C和50 °C下均显示聚脯氨酸II结构的特征谱带，而级分8中的那些谱带在50 °C下比3 °C下弱。1H nOe、13 C T1和CD数据表明AFGP组分8在低温下为伸展的“棒状”构象，在高温下变为柔性卷曲，而组分1-4为柔性棒状，具有足够的节段迁移率，可消除任何长程有序。
High-field proton and13C NMR spectroscopy has been used to test and refine the recent proposal, based on vacuum uv circular dichroism results, of a threefold left-handed helical conformation for antifreeze glycoprotein (AFGP). Partial assignment of the protons of the glycotripeptide repeating unit has been made by comparison with spectra of model compounds, by selective decoupling, and by measurements of nuclear Overhauser effect (nOe). At 40 °C, AFGP fraction 8 (Mr2600) shows 2-Hz linewidths which broaden at lower temperature. Neither1H nor13C chemical shifts depend strongly on temperature, suggesting no abrupt conformational transition. The nOe between alanine α and β protons vary with temperature and with field strength, from small positive enhancements at 50 °C and 80 MHz to large negative effects at 3 °C and 300 MHz, indicating a substantial change of rotational correlation time with temperature. The higher-molecular-weight fraction 1–4 shows negative nOe at all temperatures. The CD spectra of fraction 1–4 show bands characteristic of the polyproline II structure at both 3 and 50 °C, while those bands in fraction 8 are weaker at 50 than 3 °C. The1H nOe, the13C T1, and CD data are interpreted as indicating that AFGP fraction 8 is an extended “rod-like” conformation at low temperature which becomes a flexible coil at high temperature, while fraction 1–4 is a flexible rod with sufficient segmental mobility to eliminate any long-range order.