Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, Lille, France.
Inserm, Université de Lille, CHU Lille, LIRIC UMR 995, Lille, France.
Biochem Biophys Res Commun. 2018 Dec 2;506(4):812-818. doi: 10.1016/j.bbrc.2018.10.138. Epub 2018 Oct 30.
The CYS domain occurs in multiple copies in many gel-forming mucins. It is believed that CYS domains can interact with each other in a reversible manner, suggesting a key role of the domain in gel formation. This domain always contains in its amino-terminal sequence the C-mannosylation motif WXXW, but whether the CYS domain is C-mannosylated is debated, and the putative role of C-mannosylation of the domain is unclear. We prepared recombinant CYS domains of the human mucin MUC5B with (WXXW→AXXW) and without a single amino acid mutation and mini-5B mucins made of a large Ser/Thr/Pro region flanked by two CYS domains with the WXXW motif or with the mutated AXXW motif on the first, second or both CYS domains. We found that the single CYS domain and the two CYS domains of mini-5B mucin must be C-mannosylable for the efficient maturation and secretion of the recombinant molecules; otherwise, they are retained in the cell and co-localized with a resident enzyme of the endoplasmic reticulum.
CYS 结构域存在于许多形成凝胶的粘蛋白中，其重复出现。据信，CYS 结构域可以以可逆的方式相互作用，这表明该结构域在凝胶形成中具有关键作用。该结构域的氨基末端序列始终包含 C-甘露糖化基序 WXXW，但 CYS 结构域是否被 C-甘露糖化存在争议，且该结构域的 C-甘露糖化的假定作用尚不清楚。我们制备了具有（WXXW→AXXW）和单个氨基酸突变的人粘蛋白 MUC5B 的重组 CYS 结构域，以及由第一个、第二个或两个 CYS 结构域上具有 WXXW 基序或突变的 AXXW 基序的大 Ser/Thr/Pro 区域侧翼的两个 CYS 结构域的 mini-5B 粘蛋白。我们发现，单个 CYS 结构域和 mini-5B 粘蛋白的两个 CYS 结构域必须能够 C-甘露糖化，才能有效地成熟和分泌重组分子；否则，它们会在细胞中被保留，并与内质网的常驻酶共定位。
