C-terminal flanking peptide stabilized the catalytic domain of a recombinant Bacillus subtilis endo-β-1, 4-glucanase

Three proteins, Egl330, Egl326 and Egl325, which covered the catalytic domain of a Bacillus subtilis endo-β-l, 4-glucanase were expressed in Escherichia coli and purified. Egl325 was a mutant of Egl330 with the peptide sequence Arg-Glu-Asn-Ile-Arg deleted in the C-terminus and Egl326 was another mutant of Egl330 with the peptide sequence Glu-Asn-Ile-Arg deleted in the C-terminus. These three proteins displayed same optimal reaction pH and temperature. However, the thermal stability and pH stability of Egl326 and Egl325 were diminished compared to Egl330. Results of ultra violet scanning, circular dichroism and Trp fluorescence spectrometry showed that the absence of the short peptide at the C-terminus of Egl330 resulted in the destabilization of the catalytic domain through affecting the folding of the protein.