ClpL is a chaperone without auxiliary factors

Caseinolytic protease L (ClpL) is a member of the heat shock protein ( H sp) 100 family, which is found mostly in Gram‐positive bacteria. Here, ClpL, a major HSP in Streptococcus pneumoniae (pneumococcus), was biochemically characterized in vitro . Recombinant ClpL shows nucleotide hydrolase, refolding, holdase and disaggregation activity using either Mg 2+ or Mn 2+ and does not require the DnaK system for chaperone activity. ClpL exhibits two features distinct from other HSP 100 family proteins: (a) Mn 2+ enhances hydrolase activity, as well as chaperone activity; and (b) NTP ase activity. ClpL forms a hexamer in the presence of ADP , ATP and ATP ‐γ‐S. Mutational analysis using double‐mutant proteins mutated at the two Walker A motifs (K127A/T128A and K458A/T459A) revealed that both nucleotide‐binding domains are involved in chaperone activity, ATP hydrolase activity and hexamerization. Overall, pneumococcal ClpL is a unique Mn 2+ ‐dependent H sp100 family member that has chaperone activity without other co‐chaperones.