Agirre Aitziber, Lorizate Maier, Nir Shlomo, Nieva José L
Unidad de Biofísica (CSIC-UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080 Bilbao, Spain.
Biochim Biophys Acta. 2008 Nov;1778(11):2621-6. doi: 10.1016/j.bbamem.2008.06.013. Epub 2008 Jun 25.
Enterovirus 2B viroporin has been involved in membrane permeabilization processes occurring late during cell infection. Even though 2B lacks an obvious signal sequence for translocation, the presence of a Lys-based amphipathic domain suggests that this product bears the intrinsic capacity for partitioning into negatively charged cytofacial membrane surfaces. Pore formation by poliovirus 2B attached to a maltose-binding protein (MBP) has been indeed demonstrated in pure lipid vesicles, a fact supporting spontaneous insertion into and direct permeabilization of membranes. Here, biochemical evidence is presented indicating that both processes are modulated by phosphatidylinositol and phosphatidylserine, the main anionic phospholipids existing in membranes of target organelles. Insertion into lipid monolayers and partitioning into phospholipid bilayers were sustained by both phospholipids. However, MBP-2B inserted into phosphatidylserine bilayers did not promote membrane permeabilization and addition of this lipid inhibited the leakage observed in phosphatidylinositol vesicles. Mathematical modelling of pore formation in membranes containing increasing phosphatidylserine percentages was consistent with its inhibitory effect arising from a higher reversibility of MBP-2B surface aggregation. These results support that 2B insertion and pore-opening are mechanistically distinguishable events modulated by the target membrane anionic phospholipids.
肠道病毒2B病毒孔蛋白参与了细胞感染后期发生的膜通透化过程。尽管2B缺乏明显的易位信号序列，但基于赖氨酸的两亲结构域的存在表明该产物具有内在能力可分配到带负电荷的细胞质膜表面。事实上，附着有麦芽糖结合蛋白（MBP）的脊髓灰质炎病毒2B在纯脂质囊泡中已被证实可形成孔道，这一事实支持其能自发插入膜并直接使膜通透化。在此，给出了生化证据，表明这两个过程均受磷脂酰肌醇和磷脂酰丝氨酸的调节，这两种是靶细胞器膜中存在的主要阴离子磷脂。磷脂酰肌醇和磷脂酰丝氨酸都能使2B插入脂质单层并分配到磷脂双层中。然而，插入磷脂酰丝氨酸双层的MBP-2B并未促进膜通透化，且添加这种脂质会抑制在磷脂酰肌醇囊泡中观察到的渗漏。对含不同磷脂酰丝氨酸百分比的膜中孔道形成的数学建模表明，其抑制作用源于MBP-2B表面聚集更高的可逆性。这些结果支持2B的插入和孔开放是由靶膜阴离子磷脂调节的机制上可区分的事件。
