Brady R L, Dodson E J, Dodson G G, Lange G, Davis S J, Williams A F, Barclay A N
Department of Chemistry, University of York, United Kingdom.
Science. 1993 May 14;260(5110):979-83. doi: 10.1126/science.8493535.
The CD4 antigen is a membrane glycoprotein of T lymphocytes that interacts with major histocompatibility complex class II antigens and is also a receptor for the human immunodeficiency virus. the extracellular portion of CD4 is predicted to fold into four immunoglobulin-like domains. The crystal structure of the third and fourth domains of rat CD4 was solved at 2.8 angstrom resolution and shows that both domains have immunoglobulin folds. Domain 3, however, lacks the disulfide between the beta sheets; this results in an expansion of the domain. There is a difference of 30 degrees in the orientation between domains 3 and 4 when compared with domains 1 and 2. The two CD4 fragment structures provide a basis from which models of the overall receptor can be proposed. These models suggest an extended structure comprising two rigid portions joined by a short and possibly flexible linker region.
CD4抗原是T淋巴细胞的一种膜糖蛋白，它与主要组织相容性复合体II类抗原相互作用，也是人类免疫缺陷病毒的受体。预计CD4的细胞外部分会折叠成四个免疫球蛋白样结构域。大鼠CD4第三和第四结构域的晶体结构在2.8埃分辨率下得到解析，结果表明这两个结构域都具有免疫球蛋白折叠。然而，结构域3在β折叠之间缺乏二硫键；这导致该结构域扩张。与结构域1和2相比，结构域3和4之间的取向相差30度。这两个CD4片段结构为提出整个受体的模型提供了基础。这些模型表明其结构呈伸展状，由两个刚性部分通过一个短的、可能具有柔性的连接区域相连。
