Chromosome 3 open reading frame 38 (C3orf38) is a protein which in humans is encoded by the C3orf38 gene. The C3orf38 protein is 329 amino acids in length. A large domain of unknown function, DUF4518, encompasses majority of the C3orf38 protein. This domain is a part of the protein family pfam15008, which is thought to be involved in apoptosis regulation. This pfam15008 is the only member of the cl20886 superfamily. While the C3orf38 protein does not have any abnormal amino acid abundance as a whole, the DUF4518 has a high abundance of histidines and a low abundance of serines, according to compositional analysis.