A mutually induced conformational fit underlies Ca2+-directed interactions between calmodulin and the proximal C terminus of KCNQ4 K+ channels
Year: 2019
Type: article
Abstract: Calmodulin (CaM) conveys intracellular Ca 2+ signals to KCNQ (Kv7, "M-type") K + channels and many other ion channels. Whether this "calmodulation" involves a dramatic structural rearrangement or only slight perturbations of the CaM/KCNQ complex is as yet unclear. A consensus structural model of conformational shifts occurring between low nanomolar and physiologically high intracellular [Ca 2+ ] is still under debate. Here, we used various techniques of biophysical chemical analyses to investigate the interactions between CaM and synthetic peptides corresponding to the A and B domains of the KCNQ4 subtype. We found that in the absence of CaM, the peptides are disordered, whereas Ca 2+ /CaM imposed helical structure on both KCNQ A and B domains. Isothermal titration calorimetry revealed that Ca 2+ /CaM has higher affinity for the B domain than for the A domain of KCNQ2–4 and much higher affinity for the B domain when prebound with the A domain. X-ray crystallography confirmed that these discrete peptides spontaneously form a complex with Ca 2+ /CaM, similar to previous reports of CaM binding KCNQ-AB domains that are linked together. Microscale thermophoresis and heteronuclear single-quantum coherence NMR spectroscopy indicated the C-lobe of Ca 2+ -free CaM to interact with the KCNQ4 B domain ( K d ∼10–20 μm), with increasing Ca 2+ molar ratios shifting the CaM-B domain interactions via only the CaM C-lobe to also include the N-lobe. Our findings suggest that in response to increased Ca 2+ , CaM undergoes lobe switching that imposes a dramatic mutually induced conformational fit to both the proximal C terminus of KCNQ4 channels and CaM, likely underlying Ca 2+ -dependent regulation of KCNQ gating.
Source: Journal of Biological Chemistry
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
Funders: U.S. Department of Energy, University of Washington, University of Texas Southwestern Medical Center, Case Western Reserve University, Temple University, Georgia Clinical and Translational Science Alliance, Morrison Trust, National Institutes of Health, University of Texas MD Anderson Cancer Center, University of Texas Health Science Center at San Antonio, National Heart, Lung, and Blood Institute, National Cancer Institute, National Institute of General Medical Sciences, National Institute of Allergy and Infectious Diseases, National Institute of Neurological Disorders and Stroke, National Center for Advancing Translational Sciences, Office of Research Infrastructure Programs, National Institutes of Health, Argonne National Laboratory
Awards: G102163711, G107546177, Mays Cancer Center at UT Health SA, G1313983767, G1420670123, G1503161442, G1664757510, G1875996279, Retroviral capsid recognition by TRIM5alpha restriction factors, G262962599, G2784524989, G2789439763, G3075337988, Institute for Integration of Medicine & Science: A Partnership to Improve Health, G3596569584, G409777406, G4155925329, G4429385918, G4700852728, Pixel Array Detector for Macromolecular Crystallography, G5607048534, G6848031779, G78868261, G8115543733, G8384522727, Clustering of individual and diverse ion channels together into complexes, and their functional coupling, mediated by A-kinase anchoring protein 79/150 in neurons, G8656016687, G9000051782, G9000051876, G9000136434, G9000280239, G9000324485, NE-CAT: A Resource for Advanced Macromolecular Crystallography, G969889393
OpenAlex ID: W2917079697