Coxiella burnetii whole cell lysate protein identification by mass spectrometry and tandem mass spectrometry.

The whole cell lysate of Coxiella burnetii strain RSA 493 was separated by two-dimensional electrophoresis and more than 500 protein spots were found on silver-stained reference map. Spots from the gels were subjected to identification based on peptide mass fingerprinting (PMF). In order to identify additional proteins, tandem mass spectrometry (MS/MS) using electrospray and matrix-assisted laser desorption/ionization techniques was applied. The three independent approaches resulted in the identification of 197 open reading frames (ORFs). Fifty-two proteins were identified by PMF and at least with one of the MS/MS methods, 37 proteins with both MS/MS instruments, and 19 proteins with all three techniques applied. All predicted C. burnetii ORFs were compared with the Clusters of Orthologous Groups database. The data related to identified proteins were stored and indexed in a file that can be read and searched using Microsoft Access.