NMR studies of interactions between C-terminal tail of Kir2.1 channel and PDZ1,2 domains of PSD95.
Control of surface expression of inwardly rectifying potassium (Kir) channels is important for regulating membrane excitability. Kir2 channels have been shown to interact directly with PDZ-containing proteins in the postsynaptic density (PSD). These scaffold proteins, such as PSD95, bind to Kir2.1 channels via a PDZ-binding motif (T/S-x-Phi) in the C-terminal tail (SEI428). By utilizing a multidimensional solution NMR approach, we show that the previously unresolved structure of Kir2.1 tail (residues 372-428) is highly flexible. Using in vitro binding assays, we determined that shortening the flexible tail of Kir2.1 preceding the C-terminal region (residues 414-428) does not significantly disrupt PDZ binding. We also investigated which amino acids in the Kir2.1 tail associated with PSD95 PDZ1,2 by NMR spectroscopy, revealing that a stretch of 12 C-terminal amino acids is involved in interaction with both PDZ domains (residues 417-428). Deletion of the 11 amino acids preceding the C-terminal tail, Delta414-424, completely disrupts binding to PSD95 PDZ1,2. Therefore, the molecular interfaces formed between PDZ domains and Kir2.1 tail involve regions outside the previously identified binding motif (SEI428) and may be important for additional channel-specific interactions with associating PDZ-containing proteins.
Pegan
Scott
S
Structural Biology, The Salk Institute, La Jolla, California 92037, USA.
Tan
Joshua
J
Huang
Alan
A
Slesinger
Paul A
PA
Riek
Roland
R
Choe
Senyon
S
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D003598:Cytoskeletal Proteins; D000076122:Disks Large Homolog 4 Protein; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D013816:Thermodynamics
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; C489461:Kir2.1 channel; D008565:Membrane Proteins; C414604:PDZD2 protein, rat; C109245:Pdzk1 protein, rat; D010446:Peptide Fragments; D024661:Potassium Channels, Inwardly Rectifying