Proteomic characterization of Yersinia pestis virulence

Abstract

The Yersinia pestis proteome was studied as a function of temperature and calcium by two-dimensional differential gel electrophoresis. Over 4,100 individual protein spots were detected, of which hundreds were differentially expressed. A total of 43 differentially expressed protein spots, representing 24 unique proteins, were identified by mass spectrometry. Differences in expression were observed for several virulence-associated factors, including catalase-peroxidase (KatY), murine toxin (Ymt), plasminogen activator (Pla), and F1 capsule antigen (Caf1), as well as several putative virulence factors and membrane-bound and metabolic proteins. Differentially expressed proteins not previously reported to contribute to virulence are candidates for more detailed mechanistic studies, representing potential new virulence determinants.

FIG. 1.

2-D DIGE overlay image of the Y. pestis soluble proteome showing differential protein expression between two in vitro growth conditions containing different temperatures and calcium levels. Colored spots represent proteins that are more abundant at 26°C with 4 mM calcium (red), at 37°C with 0 mM calcium (blue), or in the pooled standard (green). White spots represent proteins with unaltered expression across the gel. Arrows with numbers show the locations of differentially expressed proteins identified by mass spectrometry (listed in Table 1).

FIG. 2.

DeCyder BVA output images showing differential expression of Pla (A), OmpA (B), and fructose-bisphosphate aldolase class II (C). Each panel shows three types of data output from the DeCyder software. The top sections show magnified regions of the gel image containing the protein spots. The left side shows the results at 26°C with added calcium, and the right side shows the results at 37°C without added calcium. Borders for the selected spots are shown in magenta. The middle sections show three-dimensional fluorescence intensity profiles for the individual spot volumes. The bottom sections show graphs of the normalized spot volumes from replicate gels. The circles displayed for each condition on the graphs represent single normalized spot volumes from one gel, and lines were plotted corresponding to the averaged values for the particular growth condition from multiple experiments. Data are representative of the proteins identified in Table 1.