Structure and Functional Relationship of Band 3 Protein

我们最近对带3蛋白这一典型的多跨多孔膜蛋白的研究表明，一些疏水的多肽部分不含边界脂，尽管它们的疏水性与Bound from(Hamasaki，et al.，J.Biochem)的疏水性相当。122、577-585(1997))。此外，带3蛋白的预期跨膜多肽部分并不相等，其中一些没有拓扑形成信号活性(Ota等人，Biol)。化学。273、28286-28291(1998年))。还发现，在体外生物合成过程中，跨膜多肽部分的相互多肽-多肽相互作用影响了拓扑发生信号的活性(Ota等人，Biol。化学。273、28286-28291(1998年))。有趣的是，我们还观察到了共翻译插入模式的证据，在这种模式中，内部信号-具有Nexo/Ccyt拓扑的另一序列-赋予前一亲水多肽片段跨膜处置(Ota等人，分子细胞…更多的L 2,495-503(1998年))，这表明亲水性多肽部分可以横跨膜脂双层周围的其他跨膜多肽部分(特别是与两亲性跨膜多肽部分)。很有可能推测，多跨多孔膜蛋白之间的相互多肽相互作用存在于蛋白质生物合成和质膜相交事件的整个过程中(Hamasaki等，Biochem)。细胞，Biol.76,729-733(1998)。根据这一证据，可以得出结论，疏水的跨膜多肽部分不一定与膜脂双层中的边界脂结合。因此，疏水性并不是形成多跨多跨膜蛋白跨膜片段的绝对要求。第2类部分(见J.Biochem。122,577-585(1997)；生物化学。细胞生物。79,729-733(1998))在膜脂双层中有相当大的自由度。含有第2类部分的蛋白质比只由结合了边界脂的跨膜多肽部分组成的膜蛋白具有更灵活的结构。这些柔性区域必须在底物-多肽相互作用或配体介导的膜脂双层构象变化中发挥重要作用。对其他多孔膜蛋白的进一步研究将支持这一新概念。较少

Our recent studies on band 3 protein, a typical multi-spanning polytopic membrane protein, implied that some hydrophobicpeptideportions were found as free from boundary lipids even though their hydrophobicity was comparable to that of bound from (Hamasaki, et al., J. Biochem. 122, 577-585(1997)). Moreover, the anticipated transmembrane peptide portions of band 3 protein were not equivalent to each other and some of them had no topogenic signal activities (Ota, et al., Biol. Chem. 273, 28286-28291(1998)). It was also found that topogenic signal activities were affected by the mutual peptide-peptide interactions of the transmembrane peptide portions during biosynthesis in vitro (Ota, et al., Biol. Chem. 273, 28286-28291(1998)). Intriguingly, we also observed the evidence for a mode of co-translational insertion in which an internal signal-another sequence with Nexo/Ccyt topology conferred a transmembrane disposition onto a preceding hydrophilic peptide segment (Ota, et al., Molecular Cel … More l 2, 495-503(1998)), suggesting that hydrophilic peptide portions can transverse the membrane lipid bilayer surrounded by other trasnmembrane peptide portions (especially with amphipathic transmembrane peptide portions). It is highly probable to speculated that the mutual peptide-peptide interactions of multi-spanning polytopic membrane proteins occurred throughout the protein biosynthesis and plasma membrane intersection events (Hamasaki, et al., Biochem. Cell., Biol. 76, 729-733(1998)).Based on this evidence, it can be concluded that the hydrophobic transmembrane peptide portions are not necessarily bound with boundary lipids in the membrane lipid bilayer. Thus, hydrophobicity is not an absolute requirement for the formation of a transmembrane segment in multispanning polytopic membrane proteins. Category 2 portions (see J. Biochem. 122, 577-585 (1997) ; Biochem. Cell Biol. 79, 729-733 (1998)) have considerable freedom in the membrane lipid bilayer. Proteins containing category 2 portions have a more flexible structure than membrane proteins that consist only of transmembrane peptide portions bound with boundary lipids. These flexible regions must play important roles in substrate-peptide interactions or ligand-mediated conformational change within membrane lipid bilayers. Further study on other polytopic membrane proteins would support this new concept. Less