Gros G, Lavalette D, Moll W, Gros H, Amand B, Pochon F
Proc Natl Acad Sci U S A. 1984 Mar;81(6):1710-4. doi: 10.1073/pnas.81.6.1710.
Two modes of molecular motion of carrier molecules can, in principle, lead to a facilitated transport of a substrate: translational and rotational diffusion. In the present study, which deals with the mechanism of the facilitated diffusion of H+ and O2 in solutions of earthworm hemoglobin, examples for both types of facilitation are presented. Only translational, not rotational, diffusion of earthworm hemoglobin appears to lead to a facilitated O2 flux. In contrast, substantial facilitated H+ fluxes of comparable size arise from rotational diffusion as well as from translational diffusion of this large protein. This is derived from measurements of facilitated H+ and O2 fluxes in earthworm hemoglobin solutions and determinations of the rotational and translational diffusion coefficients of earthworm hemoglobin with the help of a theoretical treatment of facilitated diffusion by rotational carrier diffusion. H+ transport by rotational protein diffusion appears to be a case where the often-postulated mechanism of facilitated transport by rotation of a carrier lends itself to experimental verification.
平动扩散和转动扩散。在本研究中，涉及蚯蚓血红蛋白溶液中H⁺和O₂的易化扩散机制，给出了这两种易化类型的实例。蚯蚓血红蛋白的易化O₂通量似乎仅由平动扩散而非转动扩散导致。相比之下，这种大蛋白质的转动扩散以及平动扩散都会产生相当大小的显著易化H⁺通量。这是通过测量蚯蚓血红蛋白溶液中的易化H⁺和O₂通量，并借助转动载体扩散对易化扩散的理论处理来测定蚯蚓血红蛋白的转动和平动扩散系数而得出的。通过转动蛋白质扩散进行的H⁺运输似乎是一个实例，即经常假定的通过载体转动实现易化运输的机制可通过实验验证。
