Correlation of an adenine-specific conformational change with the ATP-dependent peptidase activity of Escherichia coli Lon.

Escherichia coli Lon, also known as protease La, is a serine protease that is activated by ATP and other purine or pyrimidine triphosphates. In this study, we examined the catalytic efficiency of peptide cleavage as well as intrinsic and peptide-stimulated nucleotide hydrolysis in the presence of hydrolyzable nucleoside triphosphates ATP, CTP, UTP, and GTP. We observed that the k(cat) of peptide cleavage decreases with the reduction in the nucleotide binding affinity of Lon in the following order: ATP > CTP > GTP approximately UTP.

The ATP-dependent Lon protease of Mus musculus is a DNA-binding protein that is functionally conserved between yeast and mammals.

The ATP-dependent Lon protease is a multi-functional enzyme that is conserved from archae to mammalian mitochondria, which not only degrades protein substrates but also binds DNA. As a starting point toward understanding Lon function in development, the mouse Lon cDNA was cloned and the encoded protein was characterized in cultured mammalian cells, in yeast and in vitro. Mouse Lon shows 87, 40 and 33% amino acid similarity with the human, yeast and bacterial homologs, respectively.

Kinetic characterization of the peptidase activity of Escherichia coli Lon reveals the mechanistic similarities in ATP-dependent hydrolysis of peptide and protein substrates.

Lon is an ATP-dependent protease that degrades unstructured proteins. In this study, we have examined the ATP dependency of Escherichia coli Lon catalyzing the hydrolysis of a defined fluorogenic peptide known as S3. Steady-state velocity analyses of S3 degradation in the presence of ATP, or the nonhydrolyzable ATP analogue AMPPNP, indicate a sequential mechanism, and the k(cat) of the reaction was 7-fold higher in the presence of ATP.