Sructural study of the M4 Immune Evasion Protein

溶液核磁共振是表征蛋白质和不超过200-300个氨基酸残基的蛋白质复合体结构的有力工具，但难以获得大量适当折叠、同位素丰富的蛋白质，这使得这种方法对m04蛋白质构成了挑战。然而，我们已经能够获得该体系几乎完整的主链共振指定以及有限的酰胺-酰胺NOE数据。使用程序Rosetta的建模技术的最新进展原则上使根据这种化学位移和有限的NOE信息对蛋白质的结构进行建模成为可能。Rosetta隐含的物理真实能量函数可以区分天然和非天然蛋白质构象，化学位移和NOE信息强烈地缩小了构象空间的允许区域。从这种方法中衍生出了m04的精炼模型，揭示了一种与常见的免疫球蛋白折叠大致相似的结构，但含有许多新的元素。根据序列同源性，新结构被认为代表了M02-M06蛋白家族的所有成员。

Solution NMR is a powerful tool for structural characterization of proteins and protein complexes not exceeding 200-300 amino acid residues, but difficulties in obtaining large quantities of properly refolded, isotopically enriched protein make this approach challenging for the m04 protein. However, we have been able to obtain virtually complete backbone resonance assignments as well as limited amide-amide NOE data for this system. Recent advances in modeling techniques using the program Rosetta in principle make it possible to model the structure of the protein on the basis of this chemical shift and limited NOE information. The physically realistic energy function implicit to Rosetta can discriminate native from non-native protein conformations and the chemical shift and NOE information strongly reduce the permissible region of conformational space. Refined models for m04 have been derived from this approach, revealing a structure that is roughly similar to the common Igg fold, but with numerous novel elements. Based on sequence homology, the new structure is believed to be representative of all members of the m02-m06 protein family.