MTHFSD (Methenyltetrahydrofolate synthetase domain-containing protein) is a 383 amino acid protein that contains one RRM (RNA recognition motif) domain, which suggests that MTHFSD functions as a RNA-binding protein. The RRM domain consists of four strands and two helices arranged in an α/β sandwich. The gene encoding MTHFSD maps to human chromosome 16, which encodes over 900 genes and comprises nearly 3% of the human genome.