Dingwall C, Sharnick S V, Laskey R A
Cell. 1982 Sep;30(2):449-58. doi: 10.1016/0092-8674(82)90242-2.
Nucleoplasmin is the most abundant protein of the nucleus of Xenopus laevis oocytes. It rapidly enters the nucleus after being injected into oocyte cytoplasm. Partial proteolysis of the nucleoplasmin pentamer reveals two structural domains within each subunit: a relatively exposed "tail" and a protected "core." When all the "tails" have been removed from the pentamer the residual "core" remains pentameric. This pentameric core fails to enter the nucleus, remaining stably in the cytoplasm. A single tail region attached to the pentamer is sufficient to transport it into the nucleus. The rate of accumulation in the nucleus, but not its final extent, depends on the number of tails per pentamer. The detached (monomeric) tails rapidly accumulate in the oocyte nucleus, indicating that the tail structure is sufficient for selective accumulation. Pentameric cores diffuse throughout the nucleus but are retained when microinjected into the nucleus, indicating that the tail is necessary for entry but not for retention within the nucleus. An improved method for purification of nucleoplasmin is also described.
核质蛋白是非洲爪蟾卵母细胞核中含量最丰富的蛋白质。将其注入卵母细胞胞质后，它能迅速进入细胞核。对核质蛋白五聚体进行部分蛋白酶解后发现，每个亚基内有两个结构域：一个相对暴露的“尾部”和一个受保护的“核心”。当五聚体上所有的“尾部”都被去除后，剩余的“核心”仍保持五聚体状态。这种五聚体核心无法进入细胞核，而是稳定地留在细胞质中。连接在五聚体上的单个尾部区域就足以将其转运到细胞核中。在细胞核中的积累速率，而非最终积累程度，取决于每个五聚体的尾部数量。分离的（单体）尾部能迅速在卵母细胞核中积累，这表明尾部结构足以实现选择性积累。五聚体核心在细胞核中扩散，但显微注射到细胞核中时会被保留下来，这表明尾部是进入细胞核所必需的，但不是在细胞核内保留所必需的。本文还描述了一种改进的核质蛋白纯化方法。
