MCTP1 is a 999 amino acid multi-pass membrane protein that belongs to the MCTP family. Existing as five alternatively spliced isoforms, MCTP1 binds calcium via its C2 domains in the absence of phospholipids. The gene encoding MCTP1 maps to human chromosome 5, which contains 181 million base pairs and comprises nearly 6% of the human genome. Deletion of the p arm of chromosome 5 leads to Cri du chat syndrome, while deletion of the q arm or of chromosome 5 altogether is common in therapy-related acute myelogenous leukemias and myelodysplastic syndrome.