This gene is a member of the cytidine deaminase gene family. It is one of a group of related genes found in a cluster, thought to result from gene duplication, on chromosome 22. Members of the cluster encode proteins that are structurally and functionally related to the C to U RNA-editing cytidine deaminase APOBEC1 and inhibit retroviruses, such as HIV, by deaminating cytosine residues in nascent retroviral cDNA.