液泡H-ATPases(V-ATPases)酸化所有真核细胞中的几种细胞器,并在细胞类型的子集中通过质膜输出质子。V-ATP酶是由外周亚复合物组成的多亚基酶,V1,即暴露于细胞质和完整的膜亚复合物,Vo,包含质子孔。Voα亚基是最大的膜亚基,由两个结构域组成。a亚基(aNT)的N端结构域与几个V1和Vo亚基相互作用,并用于桥接V1和Vo亚复合物,而C端结构域包含八个跨膜螺旋,其中两个直接参与质子传输。虽然可以有几个V-ATPase亚基的多个亚型,在大多数生物体中,a亚基由数量最多的同工型编码。例如,人类基因组编码四种a-亚基亚型,表现出组织和细胞器特异性分布。在酿酒酵母中,两个a亚基亚型,富含高尔基体的Stv1和液泡Vph1是唯一的V-ATPase亚基亚型。当前的结构信息表明,a-亚基同种型采用类似的主链结构,但序列变异允许在运输过程中和对细胞信号的响应中进行特定的相互作用。V-ATP酶受到几种类型的环境调节,其用于将它们的活性调节到它们的细胞位置和环境要求。aNT结构域在复合物中的位置使其成为调节V1-Vo相互作用和调节酶活性的理想靶标。酵母α-亚基同种型已成为解剖调节输入与亚基同种型相互作用的范例。重要的是,含有每个a-亚基同种型的酵母V-ATP酶的结构是可用的。结合Stv1NT和Vph1NT元件的嵌合a亚基提供了有关如何整合调控输入以允许V-ATPases在不同胁迫条件下支持细胞生长的见解。尽管四种哺乳动物α-亚基亚型的功能和分布呈现额外的复杂性,显然,这些同种型的aNT结构域也受到多重调控相互作用的影响。靶向哺乳动物α-亚基亚型的调节机制,特别是aNT域,将被描述。改变的V-ATP酶功能与人类的多种疾病有关。讨论了通过同工型特异性调节相互作用调节V-ATPase亚群的可能性。
Vacuolar H+-ATPases (V-ATPases) acidify several organelles in all eukaryotic cells and export protons across the plasma membrane in a subset of cell types. V-ATPases are multisubunit enzymes consisting of a peripheral subcomplex, V1, that is exposed to the cytosol and an integral membrane subcomplex, Vo, that contains the proton pore. The Vo a-subunit is the largest membrane subunit and consists of two domains. The N-terminal domain of the a-subunit (aNT) interacts with several V1 and Vo subunits and serves to bridge the V1 and Vo subcomplexes, while the C-terminal domain contains eight transmembrane helices, two of which are directly involved in proton transport. Although there can be multiple isoforms of several V-ATPase subunits, the a-subunit is encoded by the largest number of isoforms in most organisms. For example, the human genome encodes four a-subunit isoforms that exhibit a tissue- and organelle-specific distribution. In the yeast S. cerevisiae, the two a-subunit isoforms, Golgi-enriched Stv1 and vacuolar Vph1, are the only V-ATPase subunit isoforms. Current structural information indicates that a-subunit isoforms adopt a similar backbone structure but sequence variations allow for specific interactions during trafficking and in response to cellular signals. V-ATPases are subject to several types of environmental regulation that serve to tune their activity to their cellular location and environmental demands. The position of the aNT domain in the complex makes it an ideal target for modulating V1-Vo interactions and regulating enzyme activity. The yeast a-subunit isoforms have served as a paradigm for dissecting interactions of regulatory inputs with subunit isoforms. Importantly, structures of yeast V-ATPases containing each a-subunit isoform are available. Chimeric a-subunits combining elements of Stv1NT and Vph1NT have provided insights into how regulatory inputs can be integrated to allow V-ATPases to support cell growth under different stress conditions. Although the function and distribution of the four mammalian a-subunit isoforms present additional complexity, it is clear that the aNT domains of these isoforms are also subject to multiple regulatory interactions. Regulatory mechanisms that target mammalian a-subunit isoforms, and specifically the aNT domains, will be described. Altered V-ATPase function is associated with multiple diseases in humans. The possibility of regulating V-ATPase subpopulations via their isoform-specific regulatory interactions are discussed.