Identification of bacterial proteins observed in MALDI TOF mass spectra from whole cells

Characteristic ions in the MALDI TOF mass spectra from bacterial cells have been associated with four known proteins. The proteins, observed both from cells and in filtered cellular suspensions, were isolated by HPLC and iden tified on the basis of their mass spectra and their partial amino acid sequ ence, determined using the Edman method (10-15 residues). The acid resistan ce proteins HdeA and HdeB give rise to ions near m/z 9735 and 9060 iu MALDI TOF mass spectra from cells and from extracts of both Escherichia coli 109 0 and Shigella flexneri PHS-1059. However, the proteins associated with pro teolytic cleavage by the peptidase Lep, rather than the precursor proteins, were observed, both using cells and from cellular extracts. A cold-shock p rotein, CspA, was associated with the ion near m/z 7643 from Pseudomonas ae ruginosa. Similarly, a cold-acclimation protein, CapB, was identified as th e source of the ion near m/z 7684 in P. putida, This last protein was homol ogous with a known CapB from P. fragi. While these experiments involved the detection of known or homologous proteins from typical bacteria, this same approach could also be applied to the detection of unique proteins or biom arker proteins associated with other bacteria of public health significance .