We examined the effects of G-protein beta and gamma subunit heterodimers on human alpha(1B) (N-type) Ca channels expressed in HEK293 cells. All of the known beta subunits (beta1-beta5) produced voltage-dependent inhibition of alpha(1B) Ca channels, depending on the gamma subunit found in the heterodimer. beta1-beta4 subunits inhibited Ca channels when paired with gamma1-gamma3. However, beta5 subunits only produced inhibition when paired with gamma2. In contrast, heterodimers between beta5 subunits and RGS (regulators of G-protein signaling) proteins containing GGL domains did not produce inhibition of Ca channels. However, GGL domain-containing RGS proteins (e.g., RGS6 and RGS11) did block the ability of Gbeta5/gamma2 heterodimers to inhibit Ca channels. Because all of the G-protein beta subunits are found in the nervous system, we conclude that they may all potentially participate in Ca channel inhibition. The interaction of GGL-containing RGS proteins with Gbeta5gamma2 suggests a novel way in which Ca channels can be regulated.