Mutational analysis of conserved AAA+ residues in the archaeal Lon protease from Thermoplasma acidophilum

The Lon protease from the archaeon Thermoplasma acidophilum (TaLon) is composed of an N-terminal ATPase associated with various cellular activities (AAA(+)) domain and a C-terminal Lon protease domain. Although related in sequence to the soluble Lon proteases, TaLon was shown to be membrane-bound in its native host and also when expressed in Escherichia coli. Recombinant TaLon was purified as a functional high-molecular weight complex displaying ATPase and proteolytic activity. Mutagenesis of conserved AAA(+) residues revealed that the Walker A and B motifs, and the sensor I and sensor 2' residues were essential for the ATPase activity, while the sensor 2 and the arginine finger were involved in activation of the protease domain. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.