[Stress proteins of Bifidobacterium longum NCC2705]

Stress proteins of Bifidobacterium longum strain NCC2705 were identified and characterized during stationary phase. According to the proteomic map of L. lactics IL1403 and theoretical Mr/pl of stress proteins in B. longum NCC2705 genome annotation, spots of stress proteins in gels were localized, and proteins were identified by matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) and/or ESI-MS/MS mass spectrometry. For protein identification by peptide mass fingerprinting, peptide masses were searched against database of B. longum NCC2705 by Mascot licensed in-house. 44 spots representing 8 protein entries have been identified, these proteins were hydrophilic proteins and predicted acid proteins. Spot and protein analysis revealed that post-translational modifications might be common in these proteins. Except for DnaJ, the stress proteins were encoded by genes with CAI value above 0.5, and represented a large proportion of the most abundant proteins. Moreover, the results of scavenging effects on free radicals in vitro showed that B. longum NCC2705 can inhibit fatty acid oxidation and scavenge DPPH, but they scavenge weakly active oxygen free radicals. We identified a key protein that can reverse oxidative damage to proteins and lipids: alkyl hydroperoxide reductase (ahpC, BL0615)synthesized under our experimental conditions.