Self-interacting domains in the C terminus of a cation-Cl- cotransporter described for the first time.
The first isoform of the Na+-K+-Cl- cotransporter (NKCC1), a widely distributed member of the cation-Cl- cotransporter superfamily, plays key roles in many physiological processes by regulating the ion and water content of animal cells and by sustaining electrolyte secretion across various epithelia. Indirect studies have led to the prediction that NKCC1 operates as a dimer assembled through binding domains that are distal to the amino portion of the carrier. In this study, evidence is presented that NKCC1 possesses self-interacting properties that result in the formation of a large complex between the proximal and the distal segment of the cytosolic C terminus. Elaborate mapping studies of these segments showed that the contact sites are dispersed along the entire C terminus, and they also led to the identification of a critical interacting residue that belongs to a putative forkhead-associated binding domain. In conjunction with previous findings, our results indicate that the uncovered interacting domains are probably a major determinant of the NKCC1 conformational landscape and assembly into a high order structure. A model is proposed in which the carrier could alternate between monomeric and homo-oligomeric units via chemical- or ligand-dependent changes in conformational dynamics.
Simard
Charles F
CF
Nephrology Research Group, Department of Medicine, Faculty of Medicine, Laval University, Québec, Québec G1R 2J6, Canada.
Brunet
Geneviève M
GM
Daigle
Nikolas D
ND
Montminy
Valérie
V
Caron
Luc
L
Isenring
Paul
P
D000595:Amino Acid Sequence; D015153:Blotting, Western; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007477:Ions; D008024:Ligands; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D028021:Sodium-Potassium-Chloride Symporters / Q000737:chemistry*; D064506:Solute Carrier Family 12, Member 2; D020798:Two-Hybrid System Techniques; D014867:Water / Q000737:chemistry
D017931:DNA Primers; D007477:Ions; D008024:Ligands; C578877:SLC12A2 protein, human; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D014867:Water; D005982:Glutathione Transferase