Newton A C, Keranen L M
Department of Chemistry, Indiana University, Bloomington 47405.
Biochemistry. 1994 May 31;33(21):6651-8. doi: 10.1021/bi00187a035.
The contributions of phospholipid headgroup structure, diacylglycerol, and Ca2+ in regulating the interaction of protein kinase C beta II with membranes or detergent/lipid mixed micelles were examined. Binding measurements revealed that, in the absence of diacylglycerol, protein kinase C displays no significant selectivity for headgroup structure other than change: the enzyme binds with equal affinity to phosphatidyl-L-serine, phosphatidyl-D-serine, and other monoanionic lipids such as phosphatidylglycerol. In contrast, selectivity for headgroup occurs in the presence of diacylglycerol. This second messenger increases the affinity of protein kinase C for phosphatidyl-L-serine-containing membranes or micelles by 2 orders of magnitude, but has only moderate effects on the affinity of protein kinase C for surfaces containing other anionic lipids. Ca2+ does not affect the diacylglycerol-mediated increase in protein kinase C's affinity for phosphatidylserine, but does increase the enzyme's affinity for acidic phospholipids. Lastly, ionic strength studies reveal that electrostatic interactions are the primary driving force in the interaction of protein kinase C with membranes. In the absence of either diacylglycerol or phosphatidylserine, these interactions are sufficiently weak that little binding occurs at physiological ionic strength; thus, protein kinase C is unlikely to translocate to the plasma membranes in the absence of diacylglycerol, even if intracellular Ca2+ levels are high. Our data reveal that, although there is no specificity for binding acidic lipids in the absence of diacylglycerol, specific structural elements of the L-serine headgroup are required for the high-affinity binding of protein kinase C to diacylglycerol-containing membranes.
研究了磷脂头部基团结构、二酰基甘油和Ca2+在调节蛋白激酶CβII与膜或去污剂/脂质混合胶束相互作用中的作用。结合测量结果表明，在没有二酰基甘油的情况下，蛋白激酶C除了电荷变化外，对头部基团结构没有明显的选择性：该酶与磷脂酰-L-丝氨酸、磷脂酰-D-丝氨酸以及其他单阴离子脂质（如磷脂酰甘油）具有相同的亲和力。相比之下，在二酰基甘油存在的情况下会出现对头部基团的选择性。这种第二信使使蛋白激酶C对含磷脂酰-L-丝氨酸的膜或胶束的亲和力提高了2个数量级，但对蛋白激酶C与含有其他阴离子脂质的表面的亲和力只有中等影响。Ca2+不影响二酰基甘油介导的蛋白激酶C对磷脂酰丝氨酸亲和力的增加，但确实增加了该酶对酸性磷脂的亲和力。最后，离子强度研究表明，静电相互作用是蛋白激酶C与膜相互作用的主要驱动力。在没有二酰基甘油或磷脂酰丝氨酸的情况下，这些相互作用足够弱，以至于在生理离子强度下几乎没有结合发生；因此，即使细胞内Ca2+水平很高，在没有二酰基甘油的情况下，蛋白激酶C也不太可能转运到质膜。我们的数据表明，虽然在没有二酰基甘油的情况下对酸性脂质的结合没有特异性，但L-丝氨酸头部基团的特定结构元件是蛋白激酶C与含二酰基甘油的膜进行高亲和力结合所必需的。
