Annexin-A6 presents two modes of association with phospholipid membranes. A combined QCM-D, AFM and cryo-TEM study
Annexin-A6 presents two modes of association with phospholipid membranes. A combined QCM-D, AFM and cryo-TEM study
复制标题
DOI：
10.1016/j.jsb.2009.03.007
复制
发表时间：
2009-10-01
影响因子：
3
通讯作者：
Brisson, Alain R.
中科院分区：
文献类型：
--
作者：
Buzhynskyy, Nikolay;Golczak, Marcin;Brisson, Alain R.
膜联蛋白是以Ca 2+依赖性方式结合于生物膜的可溶性蛋白质。Annexin-A6（AnxA 6）是膜联蛋白家族中独特的，因为它由两个膜联蛋白核心模块的重复组成，而所有其他膜联蛋白由单个模块组成。AnxA 6已被提出参与各种膜相关过程，包括内吞和胞吐，但AnxA 6与生物膜结合的分子机制，特别是其聚集膜的能力，仍然不清楚。为了解决这个问题，我们研究了关联的AnxA 6与模型磷脂膜相结合的技术，石英晶体微天平与耗散监测（QCM-D），（冷冻）透射电子显微镜（TEM）和原子力显微镜（AFM）。将AnxA 6的膜结合和膜聚集的性质与两个参考系统进行比较，即膜联蛋白A5（AnxA 5）（其为膜联蛋白原型）和嵌合AnxA 5-二聚体分子（其能够以对称方式聚集两个膜）。我们发现，AnxA 6提出了两种模式的协会与脂膜依赖于Ca 2+浓度。在低Ca 2+浓度（类似于60-150 μ M）下，AnxA 6通过其两个共平面膜联蛋白模块结合到膜上，并且不能结合两个单独的膜。在高Ca 2+浓度（类似于2 mM）下，AnxA 6分子能够结合两个相邻的磷脂膜，并呈现出类似于AnxA 6 3D晶体结构的构象。这些新的膜结合特性的AnxA 6可能的生物学意义进行了讨论。(C)2009 Elsevier Inc. All rights reserved.
Annexins are soluble proteins that bind to biological membranes in a Ca2+-dependent manner. Annexin-A6 (AnxA6) is unique in the annexin family as it consists of the repeat of two annexin core modules, while all other annexins consist of a single module. AnxA6 has been proposed to participate in various membrane-related processes, including endocytosis and exocytosis, yet the molecular mechanism of association of AnxA6 with biological membranes, especially its ability to aggregate membranes, is still unclear. To address this question, we studied the association of AnxA6 with model phospholipid membranes by combining the techniques of quartz crystal microbalance with dissipation monitoring (QCM-D), (cryo-) transmission electron microscopy (TEM) and atomic force microscopy (AFM). The properties of membrane binding and membrane aggregation of AnxA6 were compared to two reference systems, annexin A5 (AnxA5), which is the annexin prototype, and a chimerical AnxA5-dimer molecule, which is able to aggregate two membranes in a symmetrical manner. We show that AnxA6 presents two modes of association with lipid membranes depending on Ca2+-concentration. At low Ca2+-concentration (similar to 60-150 mu M), AnxA6 binds to membranes via its two coplanar annexin modules and is not able to associate two separate membranes. At high Ca2+-concentration (similar to 2 mM), AnxA6 molecules are able to bind two adjacent phospholipid membranes and present a conformation similar to the AnxA6 3D crystallographic structure. Possible biological implications of these novel membrane-binding properties of AnxA6 are discussed. (C) 2009 Elsevier Inc. All rights reserved.