SELDI protein expression profiling & biomarker identification of Streptococcus pneumoniae

A protein chip-based proteomics profiling platform employing SELDI-TOF mass spectrometry was used to identify differentially expressed proteins of Streptococcus pneumoniae. The bacterial pellets from the 100 ml culture were washed and resuspended in 5ml PBS supplemented with 1mM PMSF prior to sonication. The clarified cell lysates were normalized and then fractionated on protein chips for differential expression profiling. The protein chip arrays had different chramotographic properties such as metal affinity (IMAC), cation exchange (WCX2), and hydrophobic phase (H4). Profound analysis identified the 57 kDa protein as a regulatory protein based on 10 peptide matches, representing 38% of the sequence, to a putative histidine kinase from S. pyogenes.