The N-terminal sequence after residue 247 plays an important role in structure and function of Lon protease from Brevibacillus thermoruber WR-249

Previous studies on the N-terminal domain of Lon proteases have not clearly identified its function. Here we constructed randomly chosen N-terminal-truncated mutants of the Lon protease from Brevibacillus thermoruber WR-249 to elucidate the structure–function relationship of this domain. Mutants lacking amino acids from 1 to 247 of N terminus retained significant peptidase and ATPase activities, but lost ∼90% of protease activity. Further truncation of the protein resulted in the loss of all three activities. Mutants lacking amino acids 246–259 or 248–256 also lost all activities and quaternary structure. Our results indicated that amino acids 248–256 (SEVDELRAQ) are important for the full function of the Lon protease.