Protein interactions, calcium, phosphorylation, and cholesterol modulate CFTR cluster formation on membranes.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel whose dysfunction leads to intracellular accumulation of chloride ions, dehydration of cell surfaces, and subsequent damage to airway and ductal organs. Beyond its function as a chloride channel, interactions between CFTR, epithelium sodium channel, and solute carrier (SLC) transporter family membrane proteins and cytoplasmic proteins, including calmodulin and Na+/H+ exchanger regulatory factor-1 (NHERF-1), coregulate ion homeostasis. CFTR has also been observed to form mesoscale membrane clusters.

Atomic resolution map of the solvent interactions driving SOD1 unfolding in CAPRIN1 condensates.

Biomolecules can be sequestered into membrane-less compartments, referred to as biomolecular condensates. Experimental and computational methods have helped define the physical-chemical properties of condensates. Less is known about how the high macromolecule concentrations in condensed phases contribute "solvent" interactions that can remodel the free-energy landscape of other condensate-resident proteins, altering thermally accessible conformations and, in turn, modulating function.

Direct Binding of the Corrector VX-809 to Human CFTR NBD1: Evidence of an Allosteric Coupling between the Binding Site and the NBD1:CL4 Interface.

Understanding the mechanism of action of modulator compounds for the cystic fibrosis transmembrane conductance regulator (CFTR) is key for the optimization of therapeutics as well as obtaining insights into the molecular mechanisms of CFTR function. We demonstrate the direct binding of VX-809 to the first nucleotide-binding domain (NBD1) of human CFTR. Disruption of the interaction between C-terminal helices and the NBD1 core upon VX-809 binding is observed from chemical shift changes in the NMR spectra of residues in the helices and on the surface of -strands S3, S9, and S10.

Deletion of Phenylalanine 508 in the First Nucleotide-binding Domain of the Cystic Fibrosis Transmembrane Conductance Regulator Increases Conformational Exchange and Inhibits Dimerization.

Deletion of Phe-508 (F508del) in the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) results in destabilization of the domain, intramolecular interactions involving the domain, and the entire channel. The destabilization caused by F508del manifests itself in defective channel processing and channel gating defects. Here, we present NMR studies of the effect of F508del and the I539T stabilizing mutation on NBD1 dynamics, with a view to understanding these changes in stability.

Conformational changes relevant to channel activity and folding within the first nucleotide binding domain of the cystic fibrosis transmembrane conductance regulator.

Deletion of Phe-508 (F508del) in the first nucleotide binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) leads to defects in folding and channel gating. NMR data on human F508del NBD1 indicate that an H620Q mutant, shown to increase channel open probability, and the dual corrector/potentiator CFFT-001 similarly disrupt interactions between β-strands S3, S9, and S10 and the C-terminal helices H8 and H9, shifting a preexisting conformational equilibrium from helix to coil. CFFT-001 appears to interact with β-strands S3/S9/S10, consistent with docking simulations.

NMR evidence for differential phosphorylation-dependent interactions in WT and DeltaF508 CFTR.

The most common cystic fibrosis (CF)-causing mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is deletion of Phe508 (DeltaF508) in the first of two nucleotide-binding domains (NBDs). Nucleotide binding and hydrolysis at the NBDs and phosphorylation of the regulatory (R) region are required for gating of CFTR chloride channel activity. We report NMR studies of wild-type and DeltaF508 murine CFTR NBD1 with the C-terminal regulatory extension (RE), which contains residues of the R region.

CFTR regulatory region interacts with NBD1 predominantly via multiple transient helices.

The regulatory (R) region of the cystic fibrosis transmembrane conductance regulator (CFTR) is intrinsically disordered and must be phosphorylated at multiple sites for full CFTR channel activity, with no one specific phosphorylation site required. In addition, nucleotide binding and hydrolysis at the nucleotide-binding domains (NBDs) of CFTR are required for channel gating. We report NMR studies in the absence and presence of NBD1 that provide structural details for the isolated R region and its interaction with NBD1 at residue-level resolution.

The energetic cost of domain reorientation in maltose-binding protein as studied by NMR and fluorescence spectroscopy.

Maltose-binding protein (MBP) is a two-domain protein that undergoes a ligand-mediated conformational rearrangement from an "open" to a "closed" structure on binding to maltooligosaccharides. To characterize the energy landscape associated with this transition, we have generated five variants of MBP with mutations located in the hinge region of the molecule. Residual dipolar couplings, measured in the presence of a weak alignment medium, have been used to establish that the average structures of the mutant proteins are related to each other by domain rotation about an invariant axis, with the rotation angle varying from 5 degrees to 28 degrees.