The beta subunit of the L-type voltage-dependent calcium channel modifies the properties of the channel complex by both allosteric modulation of the alpha1 subunit function and by chaperoning the translocation of the alpha1 subunit to the plasma membrane. The goal of this study was to investigate the functional effect of changing the in vivo stoichiometry between the alpha1 and beta subunits by creating a dominant negative expression system in a transgenic mouse model. The high affinity P subunit-binding domain of the alpha(1) subunit was overexpressed in a cardiac-specific manner to act as a beta subunit trap. We found that the predominant beta isoform was located primarily in the membrane bound fraction of heart protein, whereas the beta(1) and beta(3) were mostly cytosolic. There was a significant diminution of the amount of beta(2) in the membrane fraction of the transgenic animals, resulting in a decrease in contractility of the heart and a decrease in L-type calcium current density in the myocyte. However, there were no distinguishable differences in, and beta(3) protein expression levels in the membrane bound fraction between transgenic and non-transgenic animals. Since the beta(1) and beta(3) isoforms only make up a small portion of the total beta subunit in the heart, slight changes in this fraction are not detectable using Western analysis. In contrast, beta(1) and beta(3) in skeletal muscle and brain, the predominant isoforms in these tissues, respectively, are membrane bound. (C) 2002 Elsevier Science (USA). All rights reserved.