So far, as yet, no general function for the UBX domain has yet emerged.

[1] Additionally, the absence of a carboxy-terminal di-glycine motif, however, indicates that UBX domains are not covalently attached to target proteins in a ubiquitin-like manner.

[2] The UBX domain comprises about 80 amino acid residues.

They are distinct structural units defining a large family of proteins that often exhibit a modular domain architecture three-dimensional structures of UBX domains reveal a close structural relationship with ubiquitin despite the lack of significant sequence homology[2] UBX domain is very similar to ubiquitin which gives us some indication of evolution.

There are ubiquitin fusion which seem to be advantageous for ribosomal subunit folding.