ATP-Dependent Lon proteases are components of the protein quality control system, which maintains a keeping of cellular proteome. Lon family consists of two subfamilies A and B, differing in subunit architecture and intracellular location. The reinterpretation of the domain organization of the non-catalytic N-terminal region of ATP-dependent LonA proteases is proposed. Using Escherichia coli LonA protease (EcLon) as an example it has been shown that a fragment (αN-domain), which is located between the N-terminal domain and the ААА+ module of that protein, is similar to the α1-domain of the first ААА+ module of chaperone-disaggregase ClpB. A coiled-coil (СС) region included in the αN-domain of LonA is similar to the M domain of ClpB chaperones, which is inserted into the α1-domain. This region is suggested to adopt the structure similar to the propeller-like (PL) domain. The typical architecture of the N-terminal region of LonA proteases is postulated to be characterized by the obligatory presence of a PL domain, included in the αN-domain, but may vary in the length and topology of the preceding N-terminal domain.