Am J Physiol Cell Physiol AJP: Gastrointestinal and Liver Physiology
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Am J Physiol Cell Physiol 275: C1384-C1390, 1998;
0363-6143/98 $5.00
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Vol. 275, Issue 5, C1384-C1390, November 1998

Molecular dissection of a basic COOH-terminal domain of Cx32 that inhibits gap junction gating sensitivity

Xiao Guang Wang and Camillo Peracchia

Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642-8711

Connexin32 (Cx32) mutants were studied by double voltage clamp in Xenopus oocytes to determine the role of basic COOH-terminal residues in gap junction channel gating by CO2 and transjunctional voltage. Replacement of five arginines with N (5R/N) or T residues in the initial COOH-terminal domain (CT1) of Cx32 enhanced CO2 sensitivity. The positive charge, rather than the R residue per se, is responsible for the inhibitory role of CT1, because mutants replacing the five R residues with K (5R/K) or H (5R/H) displayed CO2 sensitivity comparable to that of wild-type Cx32. Mutants replacing R with N residues four at a time (4R/N) showed that CO2 sensitivity is strongly inhibited by R215 and mildly by R219, whereas R220, R223, and R224 may slightly increase sensitivity. Neither the 5R/N nor the 4R/N mutants differed in voltage sensitivity from wild-type Cx32. The possibility that inhibition of gating sensitivity results from electrostatic interactions between CT1 and the cytoplasmic loop is discussed as part of a model that envisions the cytoplasmic loop of Cx32 as a key element of chemical gating.

cell communication; cell junctions; connexins; channels; acidification; Xenopus oocytes


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