The species-specific Lon-insertion domain (LID) is characteristic of Lon proteases (also known as endopeptidase La) and is fused to the AAA+ module [1]. Bacterial and eukaryotic Lons (LonA) have a LID at the N-terminal of AAA+ module; in archaeal Lons (LonB) the LID, represented in this entry, is inserted within the AAA+ module in a series of transmembrane segments known as the membrane-anchoring region (MA). In the Lon-like protease LonC, which does not have ATPase activity, the LID is also within the AAA-like module similar to LonBs; in this case, it is predicted to contain coiled-coil regions rather than transmembrane segments [1].

1: Structures of an ATP-independent Lon-like protease and its complexes with covalent inhibitors. Liao JH, Ihara K, Kuo CI, Huang KF, Wakatsuki S, Wu SH, Chang CI; Acta Crystallogr D Biol Crystallogr. 2013;69:1395-1402. PMID:23897463