Mutational effect for stability in a conserved region of thermolysin

AIMS: To investigate the mutational effect for the stability of thermolysin (TLN) in conserved regions. METHODS AND RESULTS: Mutational effects for stability at autodegradation sites of TLN in conserved region were studied. The bands of mutant TLN (34 kDa) on SDS-PAGE were decreased. However, those of mutant TLN cultivated with CaCl2 recovered to the same level as WT TLN. Dialysis study shows that these mutant TLN require more calcium ions than WT TLN. CONCLUSIONS: From these results, calcium affinity of mutant TLN in the conserved regions seem to become weak, subsequently mutant TLN were easily autodegraded in the case of low concentration of CaCl2. SIGNIFICANCE AND IMPACT OF THE STUDY: The autodegradation sites located in conserved regions of bacilli neutral proteases are important for the tertiary structure formation concerning the stability of the protein.