Varas Mariana, Sánchez-Borzone Mariela, Sánchez Julieta M, Barioglio Susana R de, Perillo María A
Biofísica-Química, Cátedra de Química Biológica, Departmento de Química, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina.
J Phys Chem B. 2008 Jun 19;112(24):7330-7. doi: 10.1021/jp7111236. Epub 2008 May 27.
The kinetics and the thermodynamics of melanin concentrating hormone (MCH) adsorption, penetration, and mixing with membrane components are reported. MCH behaved as a surface active peptide, forming stable monolayers at a lipid-free air-water interface, with an equilibrium spreading pressure, a collapse pressure, and a minimal molecular area of 11 mN/m, 13 mN/m, and 140 A (2), respectively. Additional peptide interfacial stabilization was achieved in the presence of lipids, as evidenced by the expansion observed at pi > pi sp in monolayers containing premixtures of MCH with zwitterionic or charged lipids. The MCH-monolayer association and dissociation rate constants were 9.52 x 10 (-4) microM (-1) min (-1) and 8.83 x 10 (-4) min (-1), respectively. The binding of MCH to the dpPC-water interface had a K d = 930 nM at 10 mN/m. MCH penetration in lipid monolayers occurred even up to pi cutoff = 29-32 mN/m. The interaction stability, binding orientation, and miscibility of MCH in monolayers depended on the lipid type, the MCH molar fraction in the mixture, and the molecular packing of the monolayer. This predicted its heterogeneous distribution between different self-separated membrane domains. Our results demonstrated the ability of MCH to incorporate itself into biomembranes and supports the possibility that MCH affects the activity of mechanosensitive membrane proteins through mechanisms unrelated with binding to specific receptors.
本文报道了黑色素聚集激素（MCH）吸附、渗透并与膜成分混合的动力学和热力学过程。MCH表现为一种表面活性肽，在无脂质的空气-水界面形成稳定的单分子层，其平衡铺展压力、崩溃压力和最小分子面积分别为11 mN/m、13 mN/m和140 Å（2）。在脂质存在的情况下，肽的界面稳定性增强，这在含有MCH与两性离子或带电脂质预混合物的单分子层中，π>πsp时观察到的膨胀现象中得到了证明。MCH-单分子层的缔合和解离速率常数分别为9.52×10（-4）μM（-1）min（-1）和8.83×10（-4）min（-1）。在10 mN/m时，MCH与dpPC-水界面的结合Kd = 930 nM。MCH在脂质单分子层中的渗透甚至可达π截止值= 29 - 32 mN/m。MCH在单分子层中的相互作用稳定性、结合取向和混溶性取决于脂质类型、混合物中MCH的摩尔分数以及单分子层的分子排列。这预示了其在不同自分离膜结构域之间的异质分布。我们的结果证明了MCH将自身整合到生物膜中的能力，并支持了MCH通过与特定受体结合无关的机制影响机械敏感膜蛋白活性的可能性。
