Kahana E, Flood G, Gratzer W B
Medical Research Council Muscle and Cell Motility Unit, King's College, London, England.
Cell Motil Cytoskeleton. 1997;36(3):246-52. doi: 10.1002/(SICI)1097-0169(1997)36:3<246::AID-CM5>3.0.CO;2-5.
We have prepared two fragments of the human dystrophin rod domain, each containing eight spectrin-like repeating units, by expression in Escherichia coli. The first corresponds to the central portion of the rod, the other to three repeats from the N-terminal end, fused to five repeats from the C-terminal end. The latter makes up the entire mutant rod, found in a patient with mild (Becker-type) muscular dystrophy. Both fragments were found to possess an ordered, stable structure, and had the form of short rod-like particles in the electron microscope. Molecular weight determinations by sedimentation equilibrium revealed that both polypeptides were monomeric in solution, suggesting that the dystrophin rod domain is incapable of forming an antiparallel homodimer. This supports the inference from sequence analyses [Winder et al., 1995: FEBS Lett. 369:27-33, 1996: Biochem. Soc. Trans. 24:2805] that the dystrophin rod domain lacks the arrangement of sites required for lateral self-association, and that dystrophin, unlike the other known proteins of the spectrin superfamily, may thus exist as a monomer.
我们通过在大肠杆菌中表达，制备了人抗肌萎缩蛋白杆状结构域的两个片段，每个片段包含八个血影蛋白样重复单元。第一个片段对应于杆状结构的中部，另一个片段对应于从N端开始的三个重复单元，并与从C端开始的五个重复单元融合。后者构成了在一名轻度（贝克型）肌营养不良患者中发现的整个突变杆状结构。发现这两个片段都具有有序、稳定的结构，并且在电子显微镜下呈短杆状颗粒的形式。通过沉降平衡测定分子量表明，两种多肽在溶液中均为单体，这表明抗肌萎缩蛋白杆状结构域无法形成反平行同源二聚体。这支持了序列分析[Winder等人，1995年：《欧洲生物化学会联合会快报》369:27 - 33，1996年：《生物化学会会刊》24:2805]得出的推论，即抗肌萎缩蛋白杆状结构域缺乏横向自我缔合所需的位点排列，因此与血影蛋白超家族的其他已知蛋白质不同，抗肌萎缩蛋白可能以单体形式存在。
