title: Kinetics of actin depolymerization: influence of ions, temperature, age of F-actin, cytochalasin B and phalloidin.
abstract: Actin, labelled with the fluorescent dye N-(3-pyrenyl)maleimide, was diluted below its critical concentration and depolymerization was followed by measuring the declining fluorescence intensity. The time courses of depolymerization were fitted to a sum of three exponentials. In most cases there was a fast initial phase followed by one or three slower ones. Increasing MgCl2 concentration slowed down depolymerization velocity, as did substitution of Tris-maleate buffer by phosphate buffer. Older F-actin preparations depolymerized more slowly than younger ones. Phalloidin strongly decreased depolymerization velocity even after sonication. In the presence of cytochalasin B depolymerization was more uniformly exponential than in the absence of cytochalasin B; overall depolymerization velocity was decreased by cytochalasin B. The results are discussed on the assumption that depolymerization kinetics reflect the length distribution of actin filaments during depolymerization.
mesh_terms: D000199:Actins / Q000378:metabolism*; D001665:Binding Sites / Q000187:drug effects; D001704:Biopolymers; D003571:Cytochalasin B / Q000494:pharmacology*; D003850:Deoxyribonuclease I / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D009842:Oligopeptides / Q000494:pharmacology*; D009994:Osmolar Concentration; D010590:Phalloidine / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D000199:Actins; D001704:Biopolymers; D009842:Oligopeptides; D010590:Phalloidine; D003571:Cytochalasin B; D003850:Deoxyribonuclease I