Anti-ADK monoclonal antibody, clone BU5G9

Aggregatibacter actinomycetemcomitans (Aa) is a pathogenic bacterium residing in the subgingival plaque biofilm strongly associated with the pathogenesis of periodontitis. The aim of this investigation was to study the protein differential expression of Aa when growing on biofilm compared with planktonic state using proteomic analysis by the 2D-DIGE system. Eighty-seven proteins were differentially expressed during biofilm growth (1.5-fold, p < 0.05), with 13 overexpressed and 37 down-expressed. Those repressed were mainly proteins involved in metabolism, biosynthesis, and transport. The overexpressed proteins were outer membrane proteins (OMPs) and highly immunogenic proteins such as YaeT (OMP), FtsZ, OMP39, OMP18/16, the chaperone GroEL, OMPA, adenylate kinase (Adk), and dihydrolipoamide acetyltransferase. The enrichment fractions of the OMPs from biofilm and planktonic states were obtained, and these proteins were analyzed by Western blotting with human serum from a periodontitis patient and one healthy control. These immunogenic proteins overexpressed in the biofilm may represent candidate virulence factors.

ATP participates in many cellular metabolic processes as a major substrate to supply energy. Many systems for acidic resistance (AR) under extremely acidic conditions have been reported, but the role of ATP has not been examined. To clarify whether or not ATP is necessary for the AR in Escherichia coli, the AR of mutants deficient in genes for ATP biosynthesis was investigated in this study. The deletion of purA or purB, each of which encodes enzymes to produce AMP from inosinate (IMP), markedly decreased the AR. The content of ATP in these mutants decreased rapidly at pH 2.5 compared to that of the wild type. The AR was again decreased significantly by the mutation of adk, which encoded an enzyme to produce ADP from AMP. The DNA damage in the purA and purB mutants was higher than that in the wild type. These results demonstrated that metabolic processes that require ATP participate in survival under extremely acidic conditions, and that one such system is the ATP-dependent DNA repair system.