Lührs Thorsten, Riek Roland, Güntert Peter, Wüthrich Kurt
Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule Zürich, CH-8093, Zürich, Switzerland.
J Mol Biol. 2003 Mar 7;326(5):1549-57. doi: 10.1016/s0022-2836(02)01471-7.
The NMR structure of the recombinant human doppel protein, hDpl(24-152), contains a flexibly disordered "tail" comprising residues 24-51, and a globular domain extending from residues 52 to 149 for which a detailed structure was obtained. The globular domain contains four alpha-helices comprising residues 72-80 (alpha1), 101-115 (alpha2(a)), 117-121 (alpha2(b)), and 127-141 (alpha3), and a short two-stranded anti-parallel beta-sheet comprising residues 58-60 (beta1) and 88-90 (beta2). The fold of the hDpl globular domain thus coincides nearly identically with the structure of the murine Dpl protein. There are close similarities with the human prion protein (hPrP) but, similar to the situation with the corresponding murine proteins, hDpl shows marked local differences when compared to hPrP: the beta-sheet is flipped by 180 degrees with respect to the molecular scaffold formed by the four helices, and the beta1-strand is shifted by two residues toward the C terminus. A large solvent-accessible hydrophobic cleft is formed on the protein surface between beta2 and alpha3, which has no counterpart in hPrP. The helix alpha2 of hPrP is replaced by two shorter helices, alpha2(a) and alpha2(b). The helix alpha3 is shortened by more than two turns when compared with alpha3 of hPrP, which is enforced by the positioning of the second disulfide bond in hDpl. The C-terminal peptide segment 144-149 folds back onto the loop connecting beta2 and alpha2. All but four of the 20 conserved residues in the globular domains of hPrP and hDpl appear to have a structural role in maintaining a PrP-type fold. The conservation of R76, E96, N110 and R134 in hDpl, corresponding to R148, E168, N183 and R208 in hPrP suggests that these amino acid residues might have essential roles in the so far unknown functions of PrP and Dpl in healthy organisms.
重组人多普蛋白hDpl(24 - 152)的核磁共振结构包含一个由24至51位残基组成的柔性无序“尾巴”，以及一个从52位残基延伸至149位残基的球状结构域，我们获得了该球状结构域的详细结构。球状结构域包含四个α螺旋，分别由72 - 80位残基（α1）、101 - 115位残基（α2(a)）、117 - 121位残基（α2(b)）和127 - 141位残基（α3）组成，还有一个由58 - 60位残基（β1）和88 - 90位残基（β2）组成的短的双股反平行β折叠。因此，hDpl球状结构域的折叠几乎与小鼠Dpl蛋白的结构完全一致。它与人类朊蛋白（hPrP）有密切的相似性，但是，与相应的小鼠蛋白情况类似，与hPrP相比，hDpl显示出明显的局部差异：β折叠相对于由四个螺旋形成的分子支架翻转了180度，并且β1链向C端移动了两个残基。在蛋白质表面β2和α3之间形成了一个大的溶剂可及疏水裂缝，这在hPrP中没有对应物。hPrP的α2螺旋被两个较短的螺旋α2(a)和α2(b)所取代。与hPrP的α3相比，hDpl的α3螺旋缩短了超过两圈，这是由hDpl中第二个二硫键的位置所导致的。C端肽段144 - 149折叠回到连接β2和α2的环上。hPrP和hDpl球状结构域中20个保守残基中除了4个之外，其余残基似乎在维持PrP型折叠中都具有结构作用。hDpl中R76、E96、N110和R134的保守性，对应于hPrP中的R148、E168、N183和R208，这表明这些氨基酸残基可能在健康生物体中PrP和Dpl迄今未知的功能中具有重要作用。
