| Popis: |
Studies on the nature and function of Intrinsically Disordered Proteins (IDP) over the past ten years have demonstrated the importance of IDPs in normal cellular function. The flexibility of IDPs allows one IDP to assume multiple conformations or form different protein-protein complexes, allowing a single protein to exhibit multiple functions. While many predicted IDPs have been characterized on an individual basis, the conservation of disorder between homologous proteins from different organisms has not been carefully studied. We now demonstrate that the FlgM protein from the thermophile Aquifex aeolicus exhibits significantly less disorder then the previously characterized FlgM protein from Salmonella typhimurium. FlgM is an inhibitor of the RNA transcription factor σ28, which is involved in regulation of flagella synthesis gene expression. Previous work has shown that the S. typhimurium FlgM protein is an intrinsically disordered protein, though the C-terminus becomes ordered when bound to σ28 or under crowded solution conditions. In this work, we demonstrate that, even under dilute solution conditions, that the A. aeolicus FlgM protein exhibits alpha-helical character. Furthermore, we use the fluorescent probe FlAsH to show that the H2 helix is ordered, even in the unbound state, in contrast to the S. typhimurium FlgM protein, and the H1 and H2 helices appear to be associated in the absence of the σ28 protein. Taken together, our data demonstrates that the A. aeolicus FlgM protein, while flexible, does not exhibit the intrinsically disordered nature exhibited by the S. typhimurium FlgM protein. |
