ATP-Dependent DNA Ligase Coupled to a KU-domain Protein
Look at the coupling between
the ATP-dependent DNA ligase and the Ku domain protein.
Here is what NCBI has to say about the KU domain proteins:
Notes on KU domains from NCBI: Ku-core domain, Ku-like subfamily;
composed of prokaryotic homologs of the eukaryotic DNA binding protein
Ku. The alignment includes the core domain shared by the prokaryotic
YkoV-like proteins and the eukaryotic Ku70 and Ku80. The prokaryotic
Ku homologs are predicted to form homodimers. It is proposed that the
Ku homologs are functionally associated with ATP-dependent DNA ligase
and the eukaryotic-type primase, probably as components of a
double-strand break repair system.
Note the weirdness going on with the ATP-dependent DNA ligase
(the red genes labeled as "1"). Some are much longer than others
suggesting the presence of extra domains in some of them.