Hartigan Nichola, Garrigue-Antar Laure, Kadler Karl E
Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, Stopford Building 2.205, Oxford Road, Manchester M13 9PT, United Kingdom.
J Biol Chem. 2003 May 16;278(20):18045-9. doi: 10.1074/jbc.M211448200. Epub 2003 Mar 13.
Bone morphogenetic protein-1 (BMP-1) is a shorter spliced variant of mammalian tolloid (mTld), both of which cleave the C-propeptides of type I procollagen during the synthesis of extracellular matrix collagen fibrils. The fact that BMP-1 and mTld both exhibit procollagen C-proteinase (PCP) activity and that BMP-1 is the smaller variant might indicate that BMP-1 comprises the minimal required sequences for PCP activity. BMP-1 comprises a metalloproteinase domain, three CUB domains, and an epidermal growth factor (EGF)-like domain, which is located between the second and third CUB (complement components C1r/C1s, the sea urchin protein Uegf, and BMP-1) domains. In this study we showed the following. 1) The CUB1 domain is required for secretion of the molecule. Domain swapping experiments, in which CUB1 and other CUB domains were interchanged, resulted in retention of the proteins by cells. Therefore, CUB1 and its location immediately adjacent to the metalloproteinase domain are essential for secretion of the protein. 2) Mutants lacking the EGF-like and CUB3 domains exhibited full C-proteinase activity. In contrast, mutants lacking the CUB2 domain were poor C-proteinases. 3) Further studies showed that Glu-483 on the beta4-beta5 loop of CUB2 is essential for C-proteinase activity of BMP-1. In conclusion, the study showed that the minimal domain structure for PCP activity is considerably shorter than expected and comprises the metalloproteinase domain and the CUB1 and CUB2 domains of BMP-1.
骨形态发生蛋白-1（BMP-1）是哺乳动物类 tolloid（mTld）的一种较短的剪接变体，二者在细胞外基质胶原纤维合成过程中均能切割 I 型前胶原的 C 端前肽。BMP-1 和 mTld 都具有前胶原 C 蛋白酶（PCP）活性，且 BMP-1 是较小的变体，这一事实可能表明 BMP-1 包含了 PCP 活性所需的最小序列。BMP-1 包含一个金属蛋白酶结构域、三个 CUB 结构域和一个表皮生长因子（EGF）样结构域，该 EGF 样结构域位于第二个和第三个 CUB（补体成分 C1r/C1s、海胆蛋白 Uegf 和 BMP-1）结构域之间。在本研究中，我们发现了以下几点。1）CUB1 结构域是该分子分泌所必需的。结构域交换实验中，将 CUB1 与其他 CUB 结构域互换，导致蛋白质被细胞滞留。因此，CUB1 及其紧邻金属蛋白酶结构域的位置对于蛋白质的分泌至关重要。2）缺失 EGF 样结构域和 CUB3 结构域的突变体表现出完全的 C 蛋白酶活性。相比之下，缺失 CUB2 结构域的突变体是较差的 C 蛋白酶。3）进一步研究表明，CUB2 的β4-β5 环上的 Glu-483 对于 BMP-1 的 C 蛋白酶活性至关重要。总之，该研究表明，PCP 活性所需的最小结构域结构比预期的要短得多，包括金属蛋白酶结构域以及 BMP-1 的 CUB1 和 CUB2 结构域。
