Intrinsic disorder in the C-terminal domain of the Shaker voltage-activated K channel modulates its interaction with scaffold proteins

Department of Life Sciences and Zlotowski Center for Neurosciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2007; 104(32):13022-7. DOI: 10.1073/pnas.0704059104
Source: PubMed


The interaction of membrane-embedded voltage-activated potassium channels (Kv) with intracellular scaffold proteins, such as the postsynaptic density 95 (PSD-95) protein, is mediated by the channel C-terminal segment. This interaction underlies Kv channel clustering at unique membrane sites and is important for the proper assembly and functioning of the synapse. In the current study, we address the molecular mechanism underlying Kv/PSD-95 interaction. We provide experimental evidence, based on hydrodynamic and spectroscopic analyses, indicating that the isolated C-terminal segment of the archetypical Shaker Kv channel (ShB-C) is a random coil, suggesting that ShB-C belongs to the recently defined class of intrinsically disordered proteins. We show that isolated ShB-C is still able to bind its scaffold protein partner and support protein clustering in vivo, indicating that unfoldedness is compatible with ShB-C activity. Pulldown experiments involving C-terminal chains differing in flexibility or length further demonstrate that intrinsic disorder in the C-terminal segment of the Shaker channel modulates its interaction with the PSD-95 protein. Our results thus suggest that the C-terminal domain of the Shaker Kv channel behaves as an entropic chain and support a "fishing rod" molecular mechanism for Kv channel binding to scaffold proteins. The importance of intrinsically disordered protein segments to the complex processes of synapse assembly, maintenance, and function is discussed.

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Available from: Uri Abdu, May 21, 2014
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    • "This is the first study to examine peculiarities of intrinsic disorder propensity in the large conductance calcium-activated K+ channel and its BKAPs. Several recent studies explored IDPRs in other channel types or their subunits, including the K+ voltage-gated channel [16], [64], the β-subunit of BK [65], and the NMDA receptor [66]. These IDPRs were defined mechanistically in relation to channel activity or interactions with cytoskeletal proteins. "
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    • "The column was calibrated with RNase A (13.7 kDa, 16.4 Å; where 1 Å=0.1 nM), chymotrypsinogen A (25.7 kDa, 20.9 Å), ovalbumin (44 kDa, 30.5 Å) and BSA (66.2 kDa, 35.5 Å). The results were analysed according to the method described previously [18]. "
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    • "Shortening the KCNE1 proximal C-terminus may cause the tail to be more rigid and restrict its conformational states thereby increasing its association strength with Kv7.1. A similar mechanism seems to apply in the case of the intrinsically disordered Shaker channel C-terminus (Magidovich et al, 2007). Taken together, this study reveals the specific interaction between the KCNE1 C-terminus and the Kv7.1 dimeric coiledcoil helix C, thereby providing a simple means to guide assembly of the I KS channel complex. "
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