Resumen:
ClpL belongs to the Hsp100 family of heat shock proteins. It
carries out a chaperone function and probably is also involved in
proteolysis, when it is associated with ClpP, removing damaged
and denatured proteins. During studies of acid tolerance response
in S. pneumoniae, we found that ClpL was highly induced at pH
5,6 (Cortes et al., SAIB 2003). This pH value was also responsible
for the autolysis observed in the wild type strain after 2 hours of
incubation at 37ºC (Piñas et al., SAIB 2003). To evaluate the role of
ClpL in acid-stress induced autolysis, we constructed a clpL mutant
and studied its lytic phenotype when incubated at pH 5,6. We
found that the clpL mutant did not undergo autolysis after 6 hours
of incubation compared with the wild type strain. We further
investigated the penicillin-induced autolysis of this mutant, and we
observed lysis in both the mutant and the wild-type strains. These
results suggest that ClpL is involved in the acid-induced autolysis
and that its chaperone function is not essential for the activity of
the major pneumococcal autolysin, LytA, since the clpL mutant
could still lyse in the presence of penicillin. ClpL, acting as a
chaperone, may be required to fold a protein that promotes the
acid-induced autolysis, or to remove by proteolysis a protein that
blocks this effect.