title: The voltage-dependent calcium channel beta subunit contains two stable interacting domains.
abstract: Voltage-dependent calcium channels selectively enable Ca2+ ion movement through cellular membranes. These multiprotein complexes are involved in a wide spectrum of biological processes such as signal transduction and cellular homeostasis. alpha1 is the membrane pore-forming subunit, whereas beta is an intracellular subunit that binds to alpha1, facilitating and modulating channel function. We have expressed, purified, and characterized recombinant beta3 and beta2a using both biochemical and biophysical methods, including electrophysiology, to better understand the beta family's protein structural and functional correlates. Our results indicate that the beta protein is composed of two distinct domains that associate with one another in a stable manner. The data also suggest that the polypeptide regions outside these domains are not structured when beta is not in complex with the channel. In addition, the beta structural core, comprised of just these two domains without other sequences, binds tightly to the alpha interaction domain (AID) motif, a sequence derived from the alpha1 subunit and the principal anchor site of beta. Domain II is responsible for this binding, but domain I enhances it.
authors.affiliation: Department of Biochemistry, Faculty of Life Sciences, Tel Aviv University, Sherman Bldg., Rm. 621, Ramat Aviv 69978, Israel.
authors.forename: Yarden
authors.initials: Y
authors.lastname: Opatowsky
authors.forename: Orna
authors.initials: O
authors.lastname: Chomsky-Hecht
authors.forename: Myoung-Goo
authors.initials: MG
authors.lastname: Kang
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Campbell
authors.forename: Joel A
authors.initials: JA
authors.lastname: Hirsch
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000378:metabolism; D002461:Cell Line, Transformed; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D004926:Escherichia coli / Q000378:metabolism; D007477:Ions; D008957:Models, Genetic; D010455:Peptides / Q000737:chemistry; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D015398:Signal Transduction; D013696:Temperature; D014982:Xenopus laevis
chemical_list: C491527:Cacnb2 protein, rat; C484333:Cacnb3 protein, rat; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D007477:Ions; D010455:Peptides; D011994:Recombinant Proteins; D002118:Calcium