Saxena A, Calderone R
Georgetown University School of Medicine, Washington, D.C. 20007.
Infect Immun. 1990 Feb;58(2):309-14. doi: 10.1128/iai.58.2.309-314.1990.
A C3d-binding glycoprotein was purified from the culture filtrate of Candida albicans by preparative isoelectric focusing. The protein possessed a pI of 3.9 to 4.1 and could inhibit rosetting of EAC3d (sheep erythrocytes conjugated to C3d) by pseudohyphae of C. albicans. When analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and mercaptoethanol, the protein migrated as a doublet with apparent molecular masses of 55 and 60 kilodaltons (kDa) and as a 50-kDa band in nonreducing gels. These results were observed with Aurodye stain for proteins. Western immunoblot, and concanavalin A stain, which indicates that both bands contain carbohydrate as well as antigenic determinants. The treatment of purified glycoprotein with endoglycosidase F but not endoglycosidases H, N, and O resulted in a complete conversion of the doublet into a faster-migrating broad band with an apparent molecular mass of 45 kDa. When the amino acid analysis of the C3d-binding protein was compared with that of the CR2 from B lymphocytes, significant differences were observed. These data indicate that C. albicans secretes a C3d-binding protein during growth in vitro which appears to be different from the mammalian C3d receptor.
通过制备性等电聚焦从白色念珠菌的培养滤液中纯化出一种C3d结合糖蛋白。该蛋白的等电点为3.9至4.1，能够抑制白色念珠菌假菌丝对EAC3d（与C3d结合的绵羊红细胞）的花环形成。在十二烷基硫酸钠和巯基乙醇存在下进行聚丙烯酰胺凝胶电泳分析时，该蛋白在还原条件下迁移为一条明显分子量为55和60千道尔顿（kDa）的双条带，在非还原凝胶中迁移为一条50-kDa的条带。用蛋白质金染、Western免疫印迹和伴刀豆球蛋白A染色观察到了这些结果，这表明两条带都含有碳水化合物以及抗原决定簇。用内切糖苷酶F而非内切糖苷酶H、N和O处理纯化的糖蛋白，导致双条带完全转化为一条迁移速度更快的宽带，表观分子量为45 kDa。当将C3d结合蛋白的氨基酸分析与B淋巴细胞的CR2的氨基酸分析进行比较时，观察到了显著差异。这些数据表明，白色念珠菌在体外生长过程中分泌一种C3d结合蛋白，该蛋白似乎与哺乳动物的C3d受体不同。
