Negatively regulates voltage-gated calcium channels by preventing the interaction between their alpha and beta subunits. Thereby, negatively regulates calcium channels activity at the plasma membrane and indirectly inhibits calcium-regulated exocytosis. Interacts with voltage-dependent calcium channels CACNB1, CACNB2, CACNB3 and CACNB4 beta subunits; prevents their interaction with the CACNA1C alpha subunit thereby negatively regulating the activity of the corresponding calcium channels. Truncated N-terminus.