The haloarchaeal ATP-dependent Lon protease is a membrane-bound DNA binding protein

SASTRE, DIEGO; PAGGI, ROBERTO; DE CASTRO, ROSANA

Tucumán

Congreso; Congreso anual de la SAIB; 2009

SAIB

Haloarchaea encode membrane-bound homologs of the ATP-dependent Lon protease, however, this enzyme has yet to be characterized and the functional role of Lon in Archaea is poorly understood. Previously, we cloned and sequenced the lon gene of the alkaliphilic haloarchaeoan Natrialba magadii. To determine the biochemical properties of NmLon, the enzyme was synthesised in E. coli (Ec-NmLon), it was purified and specific antibodies were generated. This allowed the demonstration of the membrane-bound localization of NmLon in E. coli and N. magadii cells. Ec-NmLon displayed ATPase activity, however, it was unable to degrade large proteins, in the presence or absence of ATP, or hydrolyse synthetic peptides. Interestingly, the NmLonB bound DNA molecules, a feature in common with the LonA subfamily but which has not been reported for archaeal LonB proteases. To understand the physiological role of the LonB protease, the expression pattern of NmLon was analysed throughout the growth curve in N. magadii cultures growing with different concentrations of yeast extract by Western blotting and protease activity determination. The membrane-associated ATP-dependent caseinolytic activity increased in nutrient limited cultures as the cells approached the stationary phase, suggesting that NmLon may participate in protein turnover during starvation.