CRYSTALLIN {GAMMA}B-I4F MUTANT PROTEIN BINDS TO {ALPHA}-CRYSTALLIN AND AFFECTS

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。一种新的小鼠突变系Clapper，从N-乙基-N-亚硝脲(ENU)诱变的小鼠中鉴定出来，患上了显性板层性白内障。白内障遮挡了视网膜眼底的图像，并在血管造影术中传递出视网膜血管的模糊荧光素图像。白内障晶状体混浊程度随小鼠年龄增长而降低。Clapper突变已被确认为GammaB-晶体蛋白基因的错义突变，它用苯丙氨酸(GammaB-I4F)取代第四个异亮氨酸残基。与野生型GammaB不同，GammaB-I4F突变蛋白在体内和体外都能与α-晶状体蛋白结合形成高分子量的复合体。圆二色谱测量表明，GammaB-I4F蛋白在高温下的稳定性低于野生型GammaB。在纯合子Clapper突变晶状体中，在白内障的区域发现深色的聚集体，增大的纤维间隙，以及无序和较小的内成熟纤维。因此，板层状白内障可能是由于晶状体中GammaB-I4F突变蛋白与α-晶状体蛋白相互作用引起的纤维间隙扩大和蛋白质聚集体的光散射效应所致。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A new mouse mutant line, Clapper, identified from N-ethyl-N-nitrosurea (ENU)-mutagenized mice, develops a dominant lamellar cataract. The cataract blocks the image of retinal fundus and transmits a fuzzy fluorescein image of retinal vasculature during angiography. The cataractous lens opacity decreases as the mice age. The Clapper mutation has been identified to be a missense mutation of the gammaB-crystallin gene that replaces the 4th isoleucine residue with a phenylalanine (gammaB-I4F). Unlike wild type gammaB, the gammaB-I4F mutant protein binds to alpha-crystallin to form high molecular weight complexes in vivo and in vitro. Circular dichroism measurements indicate that gammaB-I4F protein is less stable than wild type gammaB at high temperature. Darkly stained aggregates, enlarged interfiber spaces, and disorganized and smaller inner mature fibers were found in the regions of the cataract in homozygous Clapper mutant lenses. Thus, the lamellar cataract is likely due to the light-scattering effects of the enlarged interfiber spaces and protein aggregates caused by gammaB-I4F mutant proteins interacting with alpha-crystallin in the lens.