[Novel view of the structure of the non-catalytic N-terminal region of ATP-dependent LonA proteases].

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 (alphaN-domain), which is located between the N-terminal domain and the AAA+ module of that protein, is similar to the alpha1-domain of the first AAA+ module of chaperone-disaggregase C1pB. A coiled-coil (CC) region included in the alphaN-domain of LonA is similar to the M domain of C1pB chaperones, which is inserted into the alpha1-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 alphaN-domain, but may vary in the length and topology of the preceding N-terminal domain.