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

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。从n -乙基-n -硝基脲（ENU）诱变小鼠中鉴定出一种新的小鼠突变系Clapper，产生显性板层性白内障。白内障阻塞了视网膜眼底的图像，并在血管造影时传递了模糊的视网膜血管荧光图像。白内障晶状体混浊随着小鼠年龄的增长而减少。Clapper突变已被鉴定为γ -晶体蛋白基因的错义突变，它将第4个异亮氨酸残基替换为苯丙氨酸（γ - i4f）。与野生型γ - b不同，γ - i4f突变蛋白在体内和体外与α -晶体蛋白结合形成高分子量复合物。圆二色性测量表明，γ - i4f蛋白在高温下的稳定性低于野生型γ - b。纯合子Clapper突变型晶状体的白内障区域可见深色聚集体，纤维间间隙增大，内部成熟纤维杂乱且较小。因此，片层性白内障可能是由于晶状体中γ - i4f突变蛋白与α -晶体蛋白相互作用导致的纤维间隙扩大和蛋白质聚集的光散射效应。

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.