Hicke L
Dept of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL, USA.
Trends Cell Biol. 1999 Mar;9(3):107-12. doi: 10.1016/s0962-8924(98)01491-3.
G-protein-coupled receptors and transporters in Saccharomyces cerevisiae are modified with ubiquitin in response to ligand biding. In most cases, the proteasome does not recognize these ubiquitinated proteins. Instead, ubiquitination serves to trigger internalization and degradation of plasma membrane proteins in the lysosome-like vacuole. A number of mammalian receptors and at least one ion channel undergo ubiquitination at the plasma membrane, and this modification is required for their downregulation. Some of these cell-surface proteins appear to be degraded by both the proteasome and lysosomal proteases. Recent evidence indicates that other proteins required for receptor internalization might also be regulated by ubiquitination, suggesting that ubiquitin plays diverse roles in regulating plasma membrane protein activity.
酿酒酵母中的G蛋白偶联受体和转运蛋白会因配体结合而被泛素修饰。在大多数情况下，蛋白酶体无法识别这些泛素化蛋白。相反，泛素化作用会触发质膜蛋白在类溶酶体液泡中的内化和降解。许多哺乳动物受体和至少一种离子通道在质膜处发生泛素化，这种修饰对于它们的下调是必需的。其中一些细胞表面蛋白似乎会被蛋白酶体和溶酶体蛋白酶共同降解。最近的证据表明，受体内化所需的其他蛋白也可能受到泛素化的调节，这表明泛素在调节质膜蛋白活性方面发挥着多种作用。
