Slow Gating of Gap Junction Channels and Calmodulin

Slow Gating of Gap Junction Channels and Calmodulin Certain COOH-terminus mutants of connexin32 (Cx32) were previously shown to form channels with unusual transjuctional voltage (V j ) sensitivity when tested heterotypically in oocytes against Cx32 wild type. Junctional conductance (G j ) slowly increased by severalfold or decreases to nearly zero with V j positive or negative, respectively, at mutant side, and V j positive at mutant side reversed CO2-induced uncoupling. This suggested that the CO2-sensitive gate might be a V j -sensitive slow gate. Based on previous data for calmodulin (CaM) involvement in gap junction function, we have hypothesized that the slow gate could be a CaM-like pore plugging molecule (cork gating model). This study describes a similar behavior in heterotypic channels between Cx32 and each of four new Cx32 mutants modified in cytoplasmic-loop and/or COOH-terminus residues. The mutants are: ML/NN+3R/N, 3R/N, ML/NN and ML/EE; in these mutants, N or E replace M105 and L106, and N replace R215, R219 and R220. This study also reports that inhibition of CaM expression strongly reduces V j and CO2 sensitivities of two of the most effective mutants, suggesting a CaM role in slow and chemical gating. The Journal of Membrane Biology Springer Journals

Slow Gating of Gap Junction Channels and Calmodulin

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Copyright © 2000 by Springer-Verlag New York Inc.
Life Sciences; Biochemistry, general; Human Physiology
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