Molecular Biology, Structures And Function Of Crystallin

眼睛的组织依赖于特化蛋白质家族。晶状体中的主要蛋白质是晶状体蛋白.我们已经证明，在人类和其他物种中，晶体蛋白是通过一种名为基因重复生成的过程产生的。酶和应激蛋白等蛋白质已经被招募来在晶状体透明度方面发挥额外的结构作用。许多种类的晶体蛋白的起源和功能已被阐明。目前，我们正在调查最后一个功能未知的主要群体。这些是相关的贝塔(B)和伽马(G)晶体蛋白。这些具有应激和癌症相关功能的蛋白质的非晶状体亲属已经被鉴定出来。这包括一种在非晶状体眼组织中表达的新基因。这种“新伽马”(Gn)的基因结构结合了b和g基因家族的特征。Northern印迹检测到视网膜中GN的表达，2D凝胶和质谱仪检测到小鼠晶状体中GN蛋白的表达。重组gn正在结晶研究中。 我们已经证明GS-晶体蛋白是成人晶状体中主要的BG-晶体蛋白。在小鼠中，GS基因是OPJ白内障的基因座。OPJ小鼠为GS在控制晶状体纤维细胞结构中的作用提供了证据。重组野生型和突变型GS蛋白已被用于功能研究。OPJ中的突变蛋白包含一个对温度敏感的不稳定突变。在老鼠的体温附近，一个结构域展开，导致蛋白质变得不能溶解。重组蛋白被用于X射线结晶学和核磁共振结构研究。为了在OPJ白内障中分离错误折叠的蛋白质和功能丧失的问题，同源重组，GS基因的“敲除”小鼠已经被创造出来。目前正在研究一种纯合子-/-品系。功能丧失表型包括上皮细胞和纤维细胞的缺陷，类似于OPJ小鼠的一些(更严重的)缺陷。GS晶状体蛋白似乎在控制正常细胞形态和纤维细胞成熟方面起作用。 在某些物种中，酶被招募为晶状体蛋白。我们已经为其中之一的ETA-晶体蛋白生产了重组蛋白，这是一种视黄醛脱氢酶，在海豚(巨型)中扮演着主要的晶体蛋白的角色。已经与伯克贝克学院小组合作确定了一种晶体结构。这种结构表明，NAD(H)辅因子在结晶蛋白中被强烈结合。这与ETA-晶体蛋白可能在晶状体中起保护作用的想法是一致的，隔离NADH具有紫外线过滤器，以减少眩光并保护免受强烈阳光的损害。

Tissues of the eye depend on families of specialized proteins. In the lens, the major proteins the crystallins. We have shown that in humans and other species, crystallins have arisen by a process called Gene Recruitement. Proteins such as enzymes and stress proteins have been recruited to serve an additionl structural role in lens transparency. The origins and functions of many classes of crystallins have been elucidated. Currently we are investigating the last major group for which a function is unknown. These are the related beta(b) and gamma (g) crystallins. Non-lens relatives of these proteins with stress and cancer related functions have been identified. This includes a novel gene expressed in non-lens eye tissues. This "new gamma" (gN) has a gene structure that combines features of both b and g gene families. gN expression has been detected in retina by Northern blot and gN protein has been detected by 2D gels and mass spec in mouse lens. Recombinant gN is in crystalliization studies. We have shown that gS-crystallin is the major bg-crystallin in the adult human lens. In mouse, the gS gene is the locus of the Opj cataract. The Opj mice provide evidence for a role of gS in control of lens fiber cell structure. Recombinant wild type and mutant proteins for gS have been produced for functional studies. The mutant protein in Opj contains a temperature-sensitive destablizing mutation. Around mouse body temperature one domain unfolds and causes the protein to become insoluble. Recombinant protein is being used in both x-ray crystallographic and NMR structure studies. To separate the issues of mis-folded protein and loss-of-function in the Opj cataract, homologous recombination, "knock-out" mice for the gS gene have been created. A homozygous -/- line for crygs is now being studied. The loss of function phenotype includes defects in both epithelial and fiber cells similar to some of the (more serious) defects in the Opj mice. gS crystallin appears to have a role in control of normal cell morphology and fiber cell maturation. In some species enzymes have been recruited as crystallins. We have produced recombinant protein for one of these, eta-crystallin, which is a retinaldehyde dehydrogenase that acts as a major crystallin in elepant shrews (macroscelids). A crystal structure has been determined in collaboration with the Birkbeck College group. This structure shows that the NAD(H) cofactor is avidly bound in the crystallized protein. This is consistent with the idea that eta-crystallin may have a protective role in the lens, sequestering NADH has a UV filter to reduce glare and protect against damage from bright sunlight.