Skip to main content
. 2012 Mar 14;302(10):C1548–C1556. doi: 10.1152/ajpcell.00319.2011

Fig. 1.

Fig. 1.

A: the connexins (Cx) are composed of four transmembrane (TM) segments, two extracellular loops, a short NH2-terminus (region 1), one cytoplasmic loop linking TM2 and TM3 (region 2 and region 3), and a longer COOH-terminal tail (region 4). The numerical score (1–9) represents the prediction probability of each amino acid in a potential calmodulin (CaM) binding site. PCBS is the overall probability for the entire potential CaM binding domain (CaMBD) predicted by the CaM Target Database. The predicted CaMBD of Cx43 is located in the distal portion of the Cx43 intracellular loop (region 3). Similar to the CaMBD of Ca2+/CaM-dependent kinase II (CaMKII), the Cx43 CaMBD conforms to the 1–5-10 CaM-binding mode subclass with hydrophobic residues at positions 1, 5, and 10. In addition, they have conserved positive residues (underlined). On the other hand, there are major amino acid differences between Cx40 and Cx43/CaMKII (highlighted in gray). The corresponding Cx40 sequence does not have conserved positive residues such as K298 and K300 bracketing the hydrophobic L299 residue in CaMKII. PCBS for the corresponding region of Cx40 is 0 instead of 13 for Cx43 and 9 for CaMKII. Potential CaM binding regions corresponding to the four connexin intracellular domains are listed in the table: h, human; m, mouse; B, basic residues; Δ, hydrophobic residues; CaMBD, CaM binding domain; (Max), maximum score of CaM binding prediction for whole peptide fragment; PCBS, probability of CaM binding predicted by the CaM Target Database; * for score 1∼3; ** for score 4∼6; *** for score 7∼9, N.B., no prediction for CaM binding. B: the decline in normalized Cx43 gap junction conductance (Gj) was temporally correlated with a threefold increase in cytosolic Ca2+ concentration ([Ca2+]i) induced by 1 μM ionomycin + 1.8 mM CaCl2 saline superfusion. The Cx43-N2a cell [Ca2+]i measurements were obtained by ratiometric fura 2 imaging in independent experiments from the dual whole cell patch Gj measurements. [Ca2+]o, extracellular Ca2+ concentration. Values are means ± SE.