Family With Sequence Similarity 13, Member B (FAM13B)

C5ORF5 has 3 putative polyadenylation signals in its 3-prime UTR. The longest deduced protein contains 915 amino acids and has a calculated molecular mass of 105 kD. It contains a putative RHOGAP (ARHGAP1) domain at its N terminus and 2 bipartite nuclear localization signals. Compared with the RHOGAP domain of ARHGAP1, the RHOGAP domain of C5ORF5 has substitutions at 2 functionally critical residues, suggesting that the protein may not function as a GTPase-activating protein. The C5ORF5 splice variants have the potential to encode several truncated proteins, including proteins with internal deletions, with different C termini, and with a deletion of the N terminus, including the RHOGAP domain. Northern blot analysis detected a doublet at about 6 kb in all 6 tissues examined.