“非双层脂结构形成的倾向性”对猪心线粒体H^+-ATP酶活性的影响

THE EFFECT OF -NONBILAYER STRUCTURE FORMATION TENDENCY ON THE ACTIVITY OF RECONSTITUTED MITOCHONDRIAL H^+-ATPase

1、PC+PE重组的线粒体H^+-ATP酶,ATP水解活力及其对寡酶素的敏感性,ATP诱导电位随非双层脂PE含量增加显著增大,当PE含量为60%-80%时ATP诱导电位达最高值.2、用PC+DOPE和PC+DEPE重组的脂酶体,前者的ATP诱导电位显著高于后者,但是两种脂酶体的ATP水解活性和寡霉素敏感性没有明显差别.3、降低PH可以促进PA形式非双层结构,PC+20%PA或大豆磷脂重组的脂酶体H^+-ATP酶活性随pH降低显著增高.4、PC+20%PA和大豆磷脂重组的脂酶体膜表层流动性随透析液PH降低而降低,5、综合上述结果.我们认为“非双层脂结构形成的倾向性”的加强,可能导致一种不稳定的或柔性的膜结构的出现,使得H^+-ATP酶呈现发挥其活性的最适构象.

1、 Mitochondria H+-ATPase was reconstituted in PC+PE liposomes. ATP driven membrane potential and hydrolytic activity as well as sensitivity to oligomycin increased markedly with increasing content of nonbilayer phospholipid PE. A maximal activity was observed in the case of 60 - 80%PE containing proteoliposomes.2、 The ATP-driven membrane potential of the H--ATPase reconstituted with DOPE was much higher than that with DEPE, but there was no obvious difference between them in the ATP hydrolytic activity as well as its sensitivity to oligomycin.3、 Lowering of pH could induce the nonbilayer structure of PA. An increasing of H+-ATPase activity in PA containing or soybean phospholipid proteoliposomes was observed when the pH value of the reconstituting medium was decreased ( 8.0 -6.5)4、 The membrane fluidity of proteoliposome reconstituted with PC + 20%PA or soybean phospholipid decreased with lowering of pH value of reconstituting medium.5、 From the above mentioned results, it is tentatively suggested that the -nonbilayer lipid structure formation tendency 'could lead to a non -stabilizing or flexible membrane structrue, which may be important for the appearance of a suit able conformation of H+ - ATPase with higher enzymatic activity.