Blum M L, Down J A, Gurnett A M, Carrington M, Turner M J, Wiley D C
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts.
Nature. 1993 Apr 15;362(6421):603-9. doi: 10.1038/362603a0.
The variable domain of the trypanosome variant surface glycoprotein (VSG) ILTat 1.24 has been shown by X-ray crystallography to resemble closely the structures of VSG MITat 1.2, despite their low sequence similarity. Specific structural features of these VSGs, including substitution of carbohydrate for an alpha-helix, can be found in other VSG sequences. Thus antigenic variation in trypanosomes is accomplished by sequence variation, not gross structural alteration; the extensive sequence differences among VSGs may be required for another reason, such as the avoidance of recognition by helper T cells. Additionally, VSG sequences are found to define families, within a VSG superfamily, which have evolved in the trypanosome genome.
锥虫可变表面糖蛋白（VSG）ILTat 1.24的可变结构域经X射线晶体学研究表明，尽管其与VSG MITat 1.2的序列相似性较低，但结构却极为相似。这些VSG的特定结构特征，包括用碳水化合物取代α螺旋，在其他VSG序列中也能找到。因此，锥虫的抗原变异是通过序列变异而非总体结构改变来实现的；VSG之间广泛的序列差异可能还有其他原因，比如避免被辅助性T细胞识别。此外，在锥虫基因组中进化形成的VSG超家族内，VSG序列可定义多个家族。
