RESUMEN
<p><b>OBJECTIVE</b>To investigate the effect of ClpE on the protein expression profiles of Streptococcus pneumoniae.</p><p><b>METHODS</b>clpE-deficient Streptococcus pneumoniae strain was constructed by long flanking homology-polymerase chain reaction (LFH-PCR) and identified by PCR and sequencing. The total bacterial proteins were analyzed by two-dimensional gel electrophoresis and imaging analysis, and the differentially expressed protein spots were excised by dot-gel digestion with trypsin. Peptide mass fingerprinting (PMF) was obtained by analysis of the fragment length by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The PMF was analyzed using software to identify the proteins.</p><p><b>RESULTS</b>The number of matched protein spots of the two gels was 61%. By sequence database searching, 4 out of the 17 differential protein spots were identified, namely hypoxanthine-guanine, pyrrolidone-carboxylate peptidase1, formate-tetrahydrofolate ligase, and bifunctional protein pyrR.</p><p><b>CONCLUSION</b>clpE gene-deficient Streptococcus pneumoniae expresses fewer kinds of proteins at also lower levels than the wild-type bacteria, suggesting that ClpE allows the bacteria to adapt to different host environments by inducing the expression of special proteins.</p>