Identification of Stringent Response-Related and Potential Serological Proteins Released from Bacillus anthracis Overexpressing the RelA/SpoT Homolog, RshBant

초록

RelA and SpoT synthesize ppGpp, a key effector molecule that facilitates the adaptation of bacteria to nutrient starvation and other stresses, known as the stringent response. To investigate the role of Rsh (Bant) , a putative RelA/SpoT homolog (encoded by BAS4302) in Bacillus anthracis, we examined the alteration of the secretome profiles after the overexpression of a functional His-Rsh (Bant) protein in the B. anthracis strain Sterne at the stationary growth phase. In the ppGpp-deficient E. coli mutant strain CF1693, overexpression of Rsh (Bant) restored a ppGpp-dependent growth defect on minimal glucose media. The secretome profiles obtained using a two-dimensional electrophoresis (2-DE) analysis were altered by overexpression of Rsh (Bant) in B. anthracis. Among the 66 protein spots differentially expressed > 1.5-fold, the 29 proteins were abundant for further identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Functional categorization of those proteins implicated their involvement in various biological activities. Taken together, our results imply that overexpression of a functional His-Rsh (Bant) can lead to the increased levels of intracellular ppGpp in B. anthracis, resulting in the significant changes in its secretome profiling. The stringent response-controlled proteins identified are likely useful as potential targets for serodiagnostic applications.

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