Lundbaek J A, Maer A M, Andersen O S
Department of Physiology and Biophysics, Cornell University Medical College, New York 10021, USA.
Biochemistry. 1997 May 13;36(19):5695-701. doi: 10.1021/bi9619841.
Hydrophobic interactions between lipid bilayers and imbedded membrane proteins couple protein conformation to the mechanical properties of the bilayer. This coupling is widely assumed to account for the regulation of membrane protein function by the membrane lipids' propensity to form nonbilayer phases, which will produce a curvature stress in the bilayer. Nevertheless, there is only limited experimental evidence for an effect of bilayer curvature stress on membrane protein structure. We show that alterations in curvature stress, due to alterations in the electrostatic energy of dioleoylphosphatidylserine bilayers, modulate the structurally well-defined gramicidin A monomer <--> dimer reaction. Maneuvers that decrease the electrostatic energy of the unperturbed bilayer promote channel dissociation; we measure the change in interaction energy. The bilayer electrostatic energy thus can affect membrane protein structure by a mechanism that does not involve the electrostatic field across the bilayer, but rather electrostatic interactions among the phospholipid head groups in each monolayer which affect the bilayer curvature stress. These results provide further evidence for the importance of mechanical interactions between a bilayer and its imbedded proteins for protein structure and function.
脂质双层与嵌入膜蛋白之间的疏水相互作用将蛋白质构象与双层的机械特性联系起来。人们普遍认为这种联系是膜脂质形成非双层相的倾向对膜蛋白功能进行调节的原因，而这会在双层中产生曲率应力。然而，关于双层曲率应力对膜蛋白结构影响的实验证据有限。我们表明，由于二油酰磷脂酰丝氨酸双层静电能的改变而导致的曲率应力变化，会调节结构明确的短杆菌肽A单体⇄二聚体反应。降低未受干扰双层静电能的操作会促进通道解离；我们测量了相互作用能的变化。因此，双层静电能可以通过一种不涉及双层跨膜静电场，而是通过每个单层中磷脂头部基团之间的静电相互作用来影响双层曲率应力的机制来影响膜蛋白结构。这些结果进一步证明了双层与其嵌入蛋白之间的机械相互作用对蛋白结构和功能的重要性。
