Information-transfer in the BE-network reported in the previous paper was further investigated. When information transfer is permitted in both directions (from the N-terminus to the C-terminus of the molecule and vice versa), transfer is not straightforward and sometimes, a kind of stagnation (mini-cycle) is observed which inhibits the further progression of information-transfer. This difficulty can be overcome by structural fluctuation of the protein. All the information can then eventually enter into the closed circuit where the basic function of the protein is performed. It was found that the closed circuit is made by a fusion of appropriate mini-cycles.
Information transfer in the BE-network of protein is extended to the analysis of protein-protein interaction, including the interaction of chymotrypsin with its substrate, HVJ-TR2. A new type of information transfer, metabolic channel, which is proposed in the tryptophan synthase complex was investigated in terms of BE-network.
α1-Syntrophin, a member of dystrophin-associated proteins, is expressed at the sarcolemma and at perivascular astrocytes, and participates in protein-protein interactions through its PDZ domain. Aquaporin-4 (AQP4) is the predominant water channel protein in the brain, and also expressed at the sarcolemma of fast-twitch muscle fibers. AQP4 is concentrated in orthogonal array particles (OAPs), and its expression has been reported to be decreased at the sarcolemma of dystrophin-deficient mdx mice. We examined whether α1-syntrophin targets AQP4 at the sarcolemma. Immunohistochemistry showed that AQP4 is absent at the sarcolemma in α1-syntrophin knockout mice and that its expression is also lost from the perivascular astrocyte endfeet. On the other hand, expression of AQP4 is not decreased at the sarcolemma of the knockout mice in the neonatal stage. Moreover, AQP4 is expressed in lung, stomach, and kidney of wild-type and α1-syntrophin null mice. Our results show that α1-syntrophin is a key molecule to localize AQP4 to the sarcolemma of mature fast myofibers and astrocyte endfeet, but AQP4 is targeted to the plasma membrane by different molecules in lung, stomach, and kidney.