LOEX/CUO-recherche, Hôpital du Saint-Sacrement, Centre Hospitalier Affilié de Québec, and Département d'Ophtalmologie, Faculté de Médecine, and PROTEO, Université Laval, Québec, Canada G1S 4L8.
Langmuir. 2012 Jun 26;28(25):9680-8. doi: 10.1021/la301135z. Epub 2012 Jun 11.
Langmuir monolayers were used to characterize the influence of the physical state of phospholipid monolayers on the binding of protein Retinis Pigmentosa 2 (RP2). The binding parameters of RP2 (maximum insertion pressure (MIP), synergy and ΔΠ(0)) in monolayers were thus analyzed in the presence of phospholipids bearing increasing fatty acyl chain lengths at temperatures where their liquid-expanded (LE), liquid-condensed (LC), or solid-condensed (SC) states can be individually observed. The data show that a larger value of synergy is observed in the LC/SC states than in the LE state, independent of the fatty acyl chain length of phospholipids. Moreover, both the MIP and the ΔΠ(0) increase with the fatty acyl chain length when phospholipids are in the LC/SC state, whereas those binding parameters remain almost unchanged when phospholipids are in the LE state. This effect of the phospholipid physical state on the binding of RP2 was further demonstrated by measurements performed in the presence of a phospholipid monolayer showing a phase transition from the LE to the LC state at room temperature. The data collected are showing that very similar values of MIP but very different values of synergy and ΔΠ(0) are obtained in the LE (below the phase transition) and LC (above the phase transition) states. In addition, the binding parameters of RP2 in the LE (below the phase transition) as well as in the LC (above the phase transition) states were found to be indistinguishable from those where single LC and LE states are respectively observed. The preference of RP2 for binding phospholipids in the LC state was then confirmed by the observation of a large modification of the shape of the LC domains in the phase transition. Therefore, protein binding parameters can be strongly influenced by the physical state of phospholipid monolayers. Moreover, measurements performed with the α/β domain of RP2 strongly suggest that the β helix of RP2 plays a major role in the preferential binding of this protein to phospholipids in the LC state.
我们使用 Langmuir 单分子膜来研究磷脂单层的物理状态对视网膜色素变性 2 型蛋白（RP2）结合的影响。在不同温度下，当磷脂的酰基链长能够分别处于伸展相（LE）、凝聚相（LC）或固态凝聚相（SC）时，我们分析了 RP2 在磷脂单层中的结合参数（最大插入压（MIP）、协同性和ΔΠ(0)）。实验结果表明，无论磷脂酰基链的长度如何，LC/SC 状态下的协同性值都大于 LE 状态下的值。此外，当磷脂处于 LC/SC 状态时，MIP 和ΔΠ(0)都随着酰基链的长度增加而增加，而当磷脂处于 LE 状态时，这些结合参数几乎保持不变。在室温下，通过测量具有从 LE 相到 LC 相相变的磷脂单层，进一步证明了磷脂物理状态对 RP2 结合的影响。实验结果表明，在 LE（低于相变）和 LC（高于相变）状态下，得到了非常相似的 MIP 值，但协同性和ΔΠ(0)的值却非常不同。此外，在 LE（低于相变）以及 LC（高于相变）状态下，RP2 的结合参数与分别观察到的单个 LC 和 LE 状态下的结合参数无法区分。在相变过程中，观察到 LC 域的形状发生了很大的变化，从而证实了 RP2 优先与 LC 状态下的磷脂结合。因此，蛋白质的结合参数可能会受到磷脂单层物理状态的强烈影响。此外，对 RP2 的α/β 结构域的测量强烈表明，RP2 的β 螺旋在该蛋白优先与 LC 状态下的磷脂结合中起着重要作用。
