MOLECULAR AND BIOCHEMICAL CHARACTERIZATION OF GTP-BINDING PROTEIN

ADP-核糖基化因子结构域蛋白1（ARD 1）是 鸟嘌呤ADP核糖基化因子（ARF）家族的一员 与其他ARF不同的核苷酸结合蛋白 存在46-kDa氨基末端延伸，其充当 GTP酶激活蛋白（GAP）的ARF结构域。类似于 ARF GAP，ARD 1差距域包含锌指基序 和对活性至关重要的精氨酸残基。它不同于 其他ARF GAP与GTP结合的共价结合 结构域及其对ARD 1的ARF结构域的特异性。ARF是 据推测，在细胞内的形成中起着关键作用。 运输囊泡，并在它们从一个隔室移动到 另我们在这里报告，ARD 1在细胞中过表达，作为一种免疫抑制剂。 融合或非融合蛋白，定位于囊泡结构中， 主要集中在核周区，但发现 也遍布胞质溶胶。微观共定位和 亚细胞分级研究表明，ARD 1与 具有高尔基体和溶酶体结构的元素。ARD 1，表达 作为一种绿色荧光融合蛋白，最初与 高尔基体网络，随后定位于溶酶体。 从人肝中分离的溶酶体膜和高尔基体膜 免疫亲和性包含天然ARD 1。本地化到这些 因此，细胞器似乎不是 过度表达这些观察结果表明，与ARF相关的 蛋白质ARD 1可能在以下的形成或功能中起作用： 溶酶体和高尔基体与溶酶体之间的蛋白质运输。

ADP-ribosylation factor domain protein 1 (ARD1) is a member of the ADP-ribosylation factor (ARF) family of guanine nucleotide-binding proteins that differs from other ARFs by the presence of a 46-kDa amino-terminal extension which acts as a GTPase-activating protein (GAP) for its ARF domain. Similar to ARF GAPs, the GAP domain of ARD1 contains a zinc finger motif and arginine residues that are critical for activity. It differs from other ARF GAPs in its covalent association with the GTP-binding domain and its specificity for the ARF domain of ARD1. ARFs are presumed to play a key role in the formation of intracellular transport vesicles and in their movement from one compartment to another. We report here that ARD1 overexpressed in cells, as a fusion or nonfusion protein, is localized in vesicular structures that are concentrated mainly in the perinuclear region, but are found also throughout the cytosol. Microscopic colocalization and subcellular fractionation studies showed that ARD1 was associated with elements of Golgi and lysosomal structures. ARD1, expressed as a green fluorescent fusion protein, was initially associated with the Golgi network and subsequently localized to lysosomes. Lysosomal and Golgi membranes isolated from human liver by immunoaffinity contained native ARD1. Localization to these organelles, therefore, did not appear to be a result of overexpression. These observations suggest that the ARF-related protein ARD1 may play a role in the formation or function of lysosomes and in protein trafficking between Golgi and lysosomes.