Multiple C2 And Transmembrane Domain Containing Protein 1 (MCTP1)

MCTP1, a novel family of evolutionarily conserved C2 domain proteins with unusual Ca(2+)-dependent properties. MCTPs are composed of a variable N-terminal sequence, three C2 domains, two transmembrane regions, and a short C-terminal sequence. The invertebrate organisms Caenorhabditis elegans and Drosophila melanogaster express a single MCTP gene, whereas vertebrates express two MCTP genes (MCTP1 and MCTP2) whose primary transcripts are extensively alternatively spliced. none of the three MCTP1 C2 domains interacted with negatively charged or neutral phospholipids in the presence or absence of Ca2+. However, Ca2+ titrations monitored via intrinsic tryptophan fluorescence revealed that all three C2 domains bound Ca2+ in the absence of phospholipids with a high apparent affinity.