TAILIEUCHUNG - Báo cáo khoa học: The Thermoplasma acidophilum Lon protease has a Ser-Lys dyad active site

A gene with significant similarity to bacterial Lon proteases was identified during the sequencing of the genome of the thermoacidophilic archaeon Thermoplasma acidophilum. Protein sequence comparison revealed thatThermoplasma Lon protease (TaLon) ismore similar to theLonBproteases restricted to Gram-positive bacteria than to the widely dis-tributed bacterial LonA. | Eur. J. Biochem. 271 4361-4365 2004 FEBS 2004 doi PRIORITY PAPER The Thermoplasma acidophilum Lon protease has a Ser-Lys dyad active site Henrike Besche and Peter Zwickl Department of Structural Biology Max-Planck-Institute of Biochemistry Martinsried Germany A gene with significant similarity to bacterial Lon proteases was identified during the sequencing of the genome of the thermoacidophilic archaeon Thermoplasma acidophilum. Protein sequence comparison revealed that Thermoplasma Lon protease TaLon is more similar to the LonB proteases restricted to Gram-positive bacteria than to the widely distributed bacterial LonA. However the active site residues of the protease and ATPase domain are highly conserved in all Lon proteases. Using site-directed mutagenesis we show here that TaLon and EcLon and probably all other Lon proteases contain a Ser-Lys dyad active site. The TaLon active site mutants were fully assembled and similar to TaLon wild-type displayed an apparent molar mass of 430 kDa upon gelfiltration. This would be consistent with a hexameric complex and indeed electron micrographs of TaLon revealed ring-shaped particles although of unknown symmetry. Comparison of the ATPase activity of Lon wild-type from Thermoplasma or Escherichia coli with respective protease active site mutants revealed differences in Km and V values. This suggests that in the course of protein degradation by wild-type Lon the protease domain might influence the activity of the ATPase domain. Keywords AAA protease archaea Lon La endopeptidase Lon La protease Ser-Lys dyad. Endopeptidase La EC was the first ATP-dependent proteolytic enzyme to be identified 1 2 . Later protease La was found to be the product of the Escherichia coli lon gene 3 4 and is now mainly called Lon peptidase or protease. This can be seen by the respective entry and listed references in the MEROPS peptidase database peptidase family S16 lon protease family http .

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