Interaction of diphtheria toxin T domain with molten globule-like proteins and its implications for translocation.
The transmembrane (T) domain of diphtheria toxin has a critical role in the low pH-induced translocation of the catalytic domain (A chain) of the toxin across membranes. Here it is shown that at low pH, addition of proteins in a partly unfolded, molten globule-like conformation converted the T domain from a shallow membrane-inserted form to its transmembrane form. Fluorescence energy transfer demonstrated that molten globule-like proteins bound to the T domain. Thus, the T domain recognizes proteins that are partly unfolded and may function in translocation of the A chain as a transmembrane chaperone.
D000906:Antibodies / Q000378:metabolism; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001896:Boron Compounds / Q000276:immunology / Q000378:metabolism; D020134:Catalytic Domain; D004167:Diphtheria Toxin / Q000737:chemistry* / Q000378:metabolism*; D004735:Energy Transfer; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000737:chemistry / Q000378:metabolism; D008567:Membranes, Artificial; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism