The C-terminal domain of peptide deformylase is disordered and dispensable for activity

Upon trypsinolysis, the 18 C-terminal residues of Escherichia coli peptide deformylase were removed but the resulting form exhibited full activity. Moreover, a mutant fms gene encoding the first 145 out of the 168 residues of the enzyme was able to complement a fms(Ts) strain and exhibited full activity. Upon progressive truncation up to residue 139, both activity and stability decreased up to complete inactivation. Mutagenesis of residues of the 138-145 region highlights the importance of Leu-141 and Phe-142. N-Terminal deletions were also carried out. Beyond two residues off, the enzyme showed a dramatic instability. Finally, NMR and thermostability studies of the full-length enzyme and comparison to the 1-147 form strongly suggest that the dispensable residues are disordered in solution.