TBC1D22A (TBC1 domain family, member 22A), also known as C22orf4, is a 517 amino acid protein that contains one Rab-GAP TBC domain and is thought to function as a GTPase-activating protein for Rab family members. Multiple isoforms of TBC1D22A exist due to alternative splicing events. The gene encoding TBC1D22A maps to human chromosome 22, which houses over 500 genes and is the second smallest human chromosome.