Interaction of diphtheria toxin (fragment A) with actin.
It was shown by gel filtration and viscosity measurements that N-terminal fragment (FA) of diphtheria toxin (DT) can interact with both G- and F-actin (filamentous actin). Elution profiles on Sephadex G-100 indicated the formation of a binary complex of fragment A (FA) with globular actin monomer (G-actin), which was inhibited by gelsolin. Deoxyribonuclease I (DNase I) in turn appeared to interact with this complex. Tritiated FA was found to bind to F-actin stoichiometrically. This binding was inhibited again by gelsolin and G-actin, but not by DNase I. The binding of FA inhibited polymerization of G-actin and induced a time-dependent breakdown of F-actin under polymerization conditions. Inhibition of its ADP-ribosyltransferase activity did not have any effect on the interactions of FA with actin. FA interacted with actin also in the cell. After treatment of human umbilical vein endothelial cells (HUVEC) with biotin-labeled DT, Western blot analysis revealed predominantly the presence of actin in affinity-isolated complexes of the labeled FA. Similarly, FA was found in immunoaffinity-isolated complexes of actin.
Bektaş
Muhammet
M
Department of Biophysics, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey. muhbektas@hotmail.com
Varol
Başak
B
Nurten
Rüstem
R
Bermek
Engin
E
D000199:Actins / Q000378:metabolism*; D000818:Animals; D004167:Diphtheria Toxin / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D011817:Rabbits; D014316:Tritium; D014783:Viscosity / Q000187:drug effects
D000199:Actins; D004167:Diphtheria Toxin; D010446:Peptide Fragments; C029795:diphtheria toxin fragment A; D014316:Tritium