Gottschalk S, Waheed A, Schmidt B, Laidler P, von Figura K
University of Göttingen, Biochemie II, FRG.
EMBO J. 1989 Nov;8(11):3215-9. doi: 10.1002/j.1460-2075.1989.tb08480.x.
BHK cells expressing human lysosomal acid phosphatase (LAP) transport LAP to lysosomes as an integral membrane protein. In lysosomes LAP is released from the membrane by proteolytic processing, which involves at least two cleavages at the C terminus of LAP. The first cleavage is catalysed by a thiol proteinase at the outside of the lysosomal membrane and removes the bulk of the cytoplasmic tail of LAP. The second cleavage is catalysed by an aspartyl proteinase inside the lysosomes and releases the luminal part of LAP from the membrane-spanning domain. The first cleavage at the cytoplasmic side of the lysosomal membrane depends on acidification of lysosomes and the second cleavage inside the lysosomes depends on prior processing of the cytoplasmic tail. These results suggest that the cytoplasmic tail controls the conformation of the luminal portion of LAP and vice versa.
表达人溶酶体酸性磷酸酶（LAP）的BHK细胞将LAP作为一种整合膜蛋白转运至溶酶体。在溶酶体中，LAP通过蛋白水解加工从膜上释放，这涉及LAP C末端至少两次切割。第一次切割由溶酶体膜外侧的一种巯基蛋白酶催化，去除LAP大部分的细胞质尾巴。第二次切割由溶酶体内的一种天冬氨酰蛋白酶催化，将LAP的腔内部从跨膜结构域释放。溶酶体膜细胞质侧的第一次切割依赖于溶酶体的酸化，而溶酶体内的第二次切割依赖于细胞质尾巴的预先加工。这些结果表明，细胞质尾巴控制LAP腔内部的构象，反之亦然。
