title: Structural flexibility of CaV1.2 and CaV2.2 I-II proximal linker fragments in solution.
abstract: Voltage-dependent calcium channels (CaV) enable the inward flow of calcium currents for a wide range of cells. CaV1 and CaV2 subtype α1 subunits form the conducting pore using four repeated membrane domains connected by intracellular linkers. The domain I-II linker connects to the membrane gate (IS6), forming an α-helix, and is bound to the CaVβ subunit. Previous studies indicated that this region may or may not form a continuous helix depending on the CaV subtype, thereby modulating channel activation and inactivation properties. Here, we used small-angle x-ray scattering and ensemble modeling analysis to investigate the solution structure of these linkers, extending from the membrane domain and including the CaVβ-binding site, called the proximal linker (PL). The results demonstrate that the CaV1.2 PL is more flexible than the CaV2.2 PL, the flexibility is intrinsic and not dependent on CaVβ binding, and the flexibility can be most easily explained by the presence of conserved glycines. Our analysis also provides a robust example of investigating protein domains in which flexibility plays an essential role.
authors.affiliation: Department of Biochemistry and Molecular Biology, Institute of Structure Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.
authors.forename: Lior
authors.initials: L
authors.lastname: Almagor
authors.forename: Ram
authors.initials: R
authors.lastname: Avinery
authors.forename: Joel A
authors.initials: JA
authors.lastname: Hirsch
authors.forename: Roy
authors.initials: R
authors.lastname: Beck
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000737:chemistry*; D020864:Calcium Channels, N-Type / Q000737:chemistry*; D051528:Guanylate Kinases / Q000737:chemistry; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011817:Rabbits; D012996:Solutions
chemical_list: D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; C419385:L-type calcium channel alpha(1C); D012996:Solutions; D051528:Guanylate Kinases