Figure 3.

Domain structures for 13 branches of the nitrilase superfamily. Additional domains are found in members of seven branches. Parentheses denote domains found in only some members of the branch. In branch 4, vanins and biotinidases have carboxy-terminal domains unique to these two sub-branches and one vanin has additional full and partial nitrilase-related domains. The NAD synthetase domains of eukaryotes are always fused with a nitrilase-related domain. In contrast, only some prokaryotic NAD synthetases are fusion proteins with a nitrilase-related domain. This led to the prediction that branch 7 and 8 nitrilase domains are glutamine amidotransferases for the associated NAD synthetases (see text for details). Apolipoprotein N-acyltransferases (branch 9) always have a hydrophobic amino-terminal domain and one member is fused to an apparent dolichol phosphate mannose synthetase, which underscores the proposed function of branch 9 enzymes in post-translational modification. Nit proteins, branch 10, are found as fused Rosetta Stone proteins with Fhit in invertebrates and are coordinately expressed with separate Fhit proteins in mammals. Branch 12 enzymes are predicted to have protein substrates as they are fused to a homolog of an amino-terminal acetyltransferase.