THE ARF FAMILY AS REGULATORS OF PROTEIN SECRETION AND OTHER CELLULAR PROCESSES

ARF是一个21 kDa GTP结合调节蛋白家族;最初 根据它们作为蛋白质的能力进行描述和纯化 霍乱体外Gs α ADP核糖基化所需的辅因子 毒素大量ARF蛋白的克隆和序列分析， 其他小的（20-25 Kda）GTP结合蛋白也导致了描述 两个结构不同的低分子量GTP结合家族 蛋白质;称为“ras相关”和ARF家族。前者是 目前由至少30种不同的基因产物组成。所有 较小的GTP结合蛋白只有ARF具有确定的生物化学活性， 独立于GTP结合或水解。这项活动使 最近将ARF家族划分为真正的ARF蛋白， 结构保守的ARF相关蛋白。最近的结果表明， 人类表达至少三种不同的ARF蛋白， 在体内和体外的活性。其中一个人类ARF基因， 在cDNA文库筛选中克隆ARF 2， 能够刺激bFGF的分泌。这些结果是一致 观察到ARF高度集中在哺乳动物细胞中， 高尔基复合体和酵母中ARF 1的破坏导致分泌物 缺损ARF在生长因子或其他蛋白调节中的作用 正在积极地研究分泌。 ARF蛋白质的特定功能域正在用两种方法进行定位。 点突变和缺失突变以及抗体探针。这项工作 确定了蛋白质的一个特定区域，该区域不参与 核苷酸结合，但对ARF功能至关重要。这使得 ARF肽抑制剂的构建， 用于ARF在蛋白质分泌中作用的体外测定。

The ARFs are a family of 21 kDa GTP-binding regulatory proteins; originally described and purified based on their ability to serve as the protein cofactor required in the in vitro ADP-ribosylation of Gs alpha by cholera toxin. Cloning and sequence analyses of numerous ARF proteins as well as other small (20-25 Kda) GTPbinding proteins has resulted in the description of two structurally distinct families of low molecular weight GTP binding proteins; referred to as the "ras-related" and ARF families. The former is currently comprised of at least thirty distinct gene products. Of all the smaller GTP binding proteins only ARF has a defined biochemical activity, independent of GTP binding or hydrolysis. This activity has allowed the recent delineation of the ARF family into the bona fide ARF proteins and the structurally conserved ARF-related proteins. Recent results indicate that humans express at least three distinct ARF proteins with conserved activities both in vivo and in vitro. One of these human ARF genes, human ARF2, was cloned in a library screen of cDNAs which selected for inserts capable of stimulating the secretion of bFGF. These results are consistent with the observations that ARF is highly concentrated in mammalian cells to the Golgi complex and disruption of ARF1 in yeast results in a secretion defect. The role of ARF in the regulation of growth factor or other protein secretion is being very actively pursued. Specific functional domains of ARF proteins are being mapped with both point and deletion mutations as well as antibody probes. This work has identified a specific region of the protein which is not involved in nucleotide binding but which is critical to ARF function. This has allowed the construction of peptide inhibitors of ARF which are currently being used in in vitro assays of the role of ARF in protein secretion.