SUBCLASS-SPECIFIC SEQUENCE MOTIFS IDENTIFIED IN RAB GTPASES
SUBCLASS-SPECIFIC SEQUENCE MOTIFS IDENTIFIED IN RAB GTPASES
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DOI：
10.1016/s0968-0004(00)88939-2
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发表时间：
1995-01-01
影响因子：
13.8
通讯作者：
PALME, K
中科院分区：
文献类型：
--
作者：
MOORE, I;SCHELL, J;PALME, K
我们已经鉴定出可能参与确定 Rub 家族小 Ras-ltke GTPases 功能特异性的序列基序。 Rub 家族的成员对于转运囊泡在不同区室之间的正确运动至关重要。真核细胞l，'。 Rub家族根据序列相似性分为多个子类（编号为Rabl至Rub24），在某些情况下，已知这些子类反映了来自不同物种的成员之间的功能相似性或等同性。 Rub 家族的所有成员似乎都能够结合并水解 GTP；然而，各个亚类的成员似乎在内吞和胞吐途径中的几个不同步骤之一中特异性发挥作用。因此，Rub GTPases 具有单独的和共享的功能，这些功能可能反映在它们的序列中。 Rub GTP 酶最高度保守的残基参与核苷酸结合和水解，这是所有 Ras 样 GTP 酶共有的功能。其他区域可能包含指定各个功能的信息。其中一个区域是“效应区”，它与亚类特异性 GTP 酶激活蛋白 (GAP) 2、3 相互作用。其序列在每个 Rab 亚类中高度保守，但在功能不同的亚类 2、3 之间差异很大。我们现在已经在 Rab GTPases 中鉴定出第二个亚类特异性区域。我们根据总体相似性和理想的效应区将 Rub 序列分为亚类。我们鉴定出那些残基是一个亚类的 hwa~ font h~ 蛋白质，但在相关亚类蛋白质的同等位置上没有发现。该分析仅限于亚类[或从远缘相关的分类群中已知的成员，因为这允许鉴定亚类内最高度保守的残基。图1a中绘制的结果显示了效应子区域周围亚类特异性残基的峰，如预期的那样，但第二个主峰出现在位置100附近（代表残基100至110的“窗口”，对应于Ha-Ras4.S的螺旋3和环7；参见图1的图例）。值得注意的是，两种酵母 Rub 蛋白之间的结构域交换实验表明，该区域与效应器区域和羧基末端膜靶向信号协同作用，赋予每种 Rub 功能特异性。事实上，如此鉴定的Rub特异性结构域与图1a中的亚类特异性残基的峰之间存在显着的重合，证明了我们分析的功能意义。 Stenmark 等人 (1994) 也将-heiix 3--loop 7 鉴定为哺乳动物 Rab5 中的特异性结构域，并显示了其功能重要性 9。
We have identified sequence motifs that may be involved in determining the functional specificity of small Ras-ltke GTPases of the Rub family. Members of the Rub family are critical [or the proper movement of transport vesicles between different compartments o| eukaryotic cells l,'. The Rub family is divided into subclasses (numbered Rabl to Rub24) based on sequence similarities, in several cases these subclasses are known to reflect functional similarity or equivalence among members from different species. All members of the Rub family appear to be able to bind and hydrolyse GTP; however, members of individual subclasses appear to act specifically at one of several different steps in the endocytic and exocytic pathways. Thus, Rub GTPases have both individual and shared functions that are presumably reflected in their sequences. The most highly conserved residues of Rub GTPases are involved in nucleotide binding and hydrolysis, functions common to all Ras-like GTPases. Other regions presumably contain the information that specifies individual functions. One such region is the'effector region', which interacts with subclass-specific GTPaseactivating proteins (GAPs) 2, 3. Its sequence is highly conserved within each Rab subclass, but diverges considerably between functionally distinct subclasses 2, 3. We have now identified a second subclass-specific region in Rab GTPases.We grouped Rub sequences into subclasses on tile basis of overall similarity'and lde~ tical effector regions. We identified those residues that are hwa~ font h~ proteins of one subclass, but that are not found at the equivalent position in proteins of related subclasses. The analysis was limited to subclasses [or which members are known from distantly related taxonomic groups, as this allowed the identification of residues that are most highly conserved within the subclass. The results, plotted in Fig. la, show a peak of subclass-specific residues around the effector region as expected, but a second major peak occurs around position 100 (representing a'window'from residues 100 to 110 and corresponding to~-helix 3 and loop 7 of Ha-Ras4. S; see legend to Fig. 1). It is noteworthy that domain-swapping experiments betweeu two yeast Rub proteins showed that this region acts cooperatively with the effector region and the carboxy-terminal membrane-targeting signal to confer functional specificity to each Rub. in fact, there is notable coincidence between the Rub specificity domains thus identified and the peaks of subclass-specific residues in Fig. la, testifying to the functional significance of our analysis. Stenmark et ai.(1994) have also identified-heiix 3--loop 7 as a specificity domain in mammalian Rab5, and shown its functional importance 9.