Influence of the (1–106) fragment of Escherichia coli Lon protease on the enzyme function and DNA binding

Abstract

Bifunctional Escherichia coli LonA protease (Ec-Lon) belongs to the superfamily of AAA⁺ proteins. It is a key member of the quality control system of the cell proteome. The enzyme degrades abnormal and defective polypeptides, as well as a number of regulatory proteins, by the processive mechanism. In addition to the ATPase module and the proteolytic domain, Ec-Lon subunit includes a two-domain N-terminal noncatalytic region. A comparative study of the enzyme properties and the DNA-binding ability of full-size Ec-Lon and its form with a deletion of 106 amino acid residues at the N-end has been carried out to reveal the role of the missing fragment in the Ec-Lon function. It has been shown that the fragment does not affect the enzyme peptidase site function or the hydrolysis of the protein substrate by the processive mechanism. However, it is essential for the manifestation of proper ATPase activity and for the implementation of the conformational rearrangements in the ATPase domain, stemming from the coordination of different nucleotides or their complexes by magnesium ions. The loss of the (1–106) fragment destabilizes the active Ec-Lon structure and results in intense Ec-Lon autolysis.