Bandorowicz-Pikuła J, Pikuła S
Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
Biochimie. 1998 Jul;80(7):613-20. doi: 10.1016/s0300-9084(98)80014-x.
Annexin (Anx) VI has been implicated in mediating the endosome aggregation and vesicle fusion in secreting epithelia during exocytosis. In addition, AnxVI of porcine liver is an ATP-binding protein, and ATP in vitro modulates its interaction with membranes and cytoskeletal elements (Bandorowicz-Pikuła and Awasthi, FEBS Lett. 409 (1997) 300-306). In this study, we examined the effect of ATP on phosphatidylserine (PtdSer) aggregation in the presence of annexin and on calcium-dependent binding of protein to liposomes, and found that ATP stimulates the former process, although it increases the calcium concentration necessary for half-maximal binding of AnxVI to membranes. These results were corroborated by the experiments with fluorescent analog of ATP, in which binding of ATP to AnxVI was affected by binding of Ca2+ and/or phospholipids to the protein. Taken together they favour an idea of ATP being a functional ligand for AnxVI, which even in the relative absence of Ca2+ may modulate interaction of AnxVI with PtdSer-enriched membranes.
膜联蛋白（Anx）VI与胞吐过程中分泌上皮细胞的内体聚集和囊泡融合有关。此外，猪肝的AnxVI是一种ATP结合蛋白，体外ATP可调节其与膜和细胞骨架成分的相互作用（Bandorowicz-Pikuła和Awasthi，《欧洲生物化学学会联合会快报》409（1997）300 - 306）。在本研究中，我们检测了ATP在有膜联蛋白存在时对磷脂酰丝氨酸（PtdSer）聚集的影响以及对蛋白质与脂质体的钙依赖性结合的影响，发现ATP刺激了前一过程，尽管它增加了AnxVI与膜半最大结合所需的钙浓度。用ATP荧光类似物进行的实验证实了这些结果，其中ATP与AnxVI的结合受Ca2 +和/或磷脂与该蛋白结合的影响。综合来看，它们支持ATP是AnxVI的功能性配体这一观点，即即使在相对缺乏Ca2 +的情况下，ATP也可能调节AnxVI与富含PtdSer的膜的相互作用。
