Frank Martin, Beccati Daniela, Leeflang Bas R, Vliegenthart Johannes F G
Biognos AB, Box 8963, Göteborg 40274, Sweden.
Bijvoet Center, Division of Bio-Organic Chemistry, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands.
iScience. 2020 Aug 21;23(8):101371. doi: 10.1016/j.isci.2020.101371. Epub 2020 Jul 16.
C-Mannosylation is a relatively rare form of protein glycosylation involving the attachment of an α-mannopyranosyl residue to C-2 of the indole moiety of the amino acid tryptophan. This type of linkage was initially discovered in RNase 2 from human urine but later confirmed to be present in many other important proteins. Based on NMR experiments and extensive molecular dynamics simulations on the hundred microsecond timescale we demonstrate that, for isolated glycopeptides and denatured RNase 2, the C-linked mannopyranosyl residue exists as an ensemble of conformations, among which C is the most abundant. However, for native RNase 2, molecular dynamics and NMR studies revealed that the mannopyranosyl residue favors a specific conformation, which optimally stabilizes the protein fold through a network of hydrogen bonds and which leads to a significant reduction of the protein dynamics on the microsecond timescale. Our findings contribute to the understanding of the biological role of C-mannosylation.
C-甘露糖基化是一种相对罕见的蛋白质糖基化形式，涉及将一个α-吡喃甘露糖基残基连接到氨基酸色氨酸吲哚部分的C-2位上。这种连接类型最初是在人尿中的核糖核酸酶2中发现的，但后来证实存在于许多其他重要蛋白质中。基于在数百微秒时间尺度上的核磁共振实验和广泛的分子动力学模拟，我们证明，对于分离的糖肽和变性的核糖核酸酶2，C-连接的吡喃甘露糖基残基以构象集合的形式存在，其中C构象最为丰富。然而，对于天然的核糖核酸酶2，分子动力学和核磁共振研究表明，吡喃甘露糖基残基倾向于一种特定的构象，该构象通过氢键网络最佳地稳定蛋白质折叠，并导致蛋白质在微秒时间尺度上的动力学显著降低。我们的研究结果有助于理解C-甘露糖基化的生物学作用。
