期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：34
页码：15069-15074
DOI：10.1073/pnas.1008818107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A deficiency of functional dystrophin protein in muscle cells causes muscular dystrophy (MD). More than 50% of missense mutations that trigger the disease occur in the N-terminal actin binding domain (N-ABD or ABD1). We examined the effect of four disease-causing mutations--L54R, A168D, A171P, and Y231N--on the structural and biophysical properties of isolated N-ABD. Our results indicate that N-ABD is a monomeric, well-folded -helical protein in solution, as is evident from its -helical circular dichroism spectrum, blue shift of the native state tryptophan fluorescence, well-dispersed amide crosspeaks in 2D NMR 15N-1H HSQC fingerprint region, and rotational correlation time calculated from NMR longitudinal (T1) and transverse (T2) relaxation experiments. Compared to WT, three mutants--L54R, A168D, and A171P--show a decreased -helicity and do not show a cooperative sigmoidal melt with temperature, indicating that these mutations exist in a wide range of conformations or in a "molten globule" state. In contrast, Y231N has an -helical content similar to WT and shows a cooperative sigmoidal temperature melt but with a decreased stability. All four mutants experience serious misfolding and aggregation. FT-IR, circular dichroism, increase in thioflavin T fluorescence, and the congo red spectral shift and birefringence show that these aggregates contain intermolecular cross-{beta} structure similar to that found in amyloid diseases. These results indicate that disease-causing mutants affect N-ABD structure by decreasing its thermodynamic stability and increasing its misfolding, thereby decreasing the net functional dystrophin concentration.
