Effect of pepstatin A on structure and polymerization of intermediate filament subunit proteins in vitro.
Pepstatin A, a pentapeptide aspartyl protease inhibitor, can interact with intermediate filament (IF) subunit proteins and induce their polymerization in the absence of salt into long filaments with a rough surface and a diameter of 15-17 nm. This polymerization appears to be driven primarily by non-ionic interactions between pepstatin A and polymerization-competent forms of IF proteins, resulting in a composite filament. Proteolytic fragments of vimentin, lacking portions of only the head domain or of both the head and tail domains, failed to copolymerize with pepstatin A into long filaments under these conditions. Rather, these peptides, as well as control proteins like bovine serum albumin, were found to decorate pepstatin A polymers (filaments, ribbons, and sheets) by sticking to their surfaces. In addition to the electron microscopy experiments, UV difference spectra, ultracentrifugation, and SDS-PAGE analysis of in vitro cleavage products of vimentin obtained with HIV-1 protease all provided independent evidence for a direct association of pepstatin A with IF subunit proteins, with subsequent alterations in the IF subunit protein conformation. These data show that non-ionic interactions can substitute for the effect of salt and effectively drive the higher-order polymerization of IF subunit proteins.
Mothes
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E
Max-Planck-Institut für Zellbiologie, Ladenburg, Federal Republic of Germany.
Shoeman
R L
RL
Traub
P
P
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D016333:HIV Protease / Q000378:metabolism; D007381:Intermediate Filament Proteins / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010436:Pepstatins / Q000494:pharmacology*; D011108:Polymers; D013056:Spectrophotometry, Ultraviolet; D013552:Swine; D014407:Tumor Cells, Cultured; D014461:Ultracentrifugation; D014746:Vimentin / Q000378:metabolism
D007381:Intermediate Filament Proteins; D010436:Pepstatins; D011108:Polymers; D014746:Vimentin; C014195:Streptomyces pepsin inhibitor; D016333:HIV Protease; C031375:pepstatin