Binding of triton X-100 to diphtheria toxin, crossreacting material 45, and their fragments.
Binding of the nonionic detergent [3H]Triton X-100 by diphtheria toxin, by the nontoxic serologically related protein crossreacting material (CRM) 45, and by their respective A and B fragments has been studied. If first denatured in 0.1% sodium dodecyl sulfate, all of the proteins with the exception of fragment A bind increasing amounts of Triton X-100, reaching a maximum of more than 40 mol bound per mol of protein when the detergent concentration exceeds its critical micelle concentration. No measurable amount of Triton X-100 is bound by native toxin or its A fragment of any concentration of the detergent. Undenatured CRM45 or its B45 fragment, on the other hand, readily became inserted into Triton X-100 micelles when the detergent reaches its critical micelle concentration. The results show that the toxin molecule contains a hydrophobic domain located on the portion of the B fragment that is linked to A. This region is masked in native toxin. Based on these findings, a model is proposed to describe how fragment B facilitates the transport of the enzymically active hydrophilic fragment A across the plasma membrane to reach the cytoplasm.
D001665:Binding Sites; D001692:Biological Transport; D004167:Diphtheria Toxin / Q000378:metabolism*; D000939:Epitopes; D008954:Models, Biological; D010455:Peptides / Q000378:metabolism; D011092:Polyethylene Glycols / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012995:Solubility; D013329:Structure-Activity Relationship
D004167:Diphtheria Toxin; D000939:Epitopes; D010455:Peptides; D000644:Quaternary Ammonium Compounds; D011092:Polyethylene Glycols