Two opposite effects of cofilin on the thermal unfolding of F-actin: a differential scanning calorimetric study.
Differential scanning calorimetry was used to examine the effects of cofilin on the thermal unfolding of actin. Stoichiometric binding increases the thermal stability of both G- and F-actin but at sub-saturating concentrations cofilin destabilizes F-actin. At actin:cofilin molar ratios of 1.5-6 the peaks corresponding to stabilized (66-67 degrees C) and destabilized (56-57 degrees C) F-actin are observed simultaneously in the same thermogram. Destabilizing effects of sub-saturating cofilin are highly cooperative and are observed at actin:cofilin molar ratios as low as 100:1. These effects are abolished by the addition of phalloidin or aluminum fluoride. Conversely, at saturating concentrations, cofilin prevents the stabilizing effects of phalloidin and aluminum fluoride on the F-actin thermal unfolding. These results suggest that cofilin stabilizes those actin subunits to which it directly binds, but destabilizes F-actin with a high cooperativity in neighboring cofilin-free regions.
Dedova
Irina V
IV
Muscle Research Unit, Department of Anatomy and Histology, The University of Sydney, NSW 2006 Sydney, Australia.
Nikolaeva
Olga P
OP
Mikhailova
Valeria V
VV
dos Remedios
Cris G
CG
Levitsky
Dmitrii I
DI
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000737:chemistry*; D017607:Aluminum Compounds / Q000494:pharmacology; D002152:Calorimetry, Differential Scanning; D004355:Drug Stability; D005459:Fluorides / Q000494:pharmacology; D008840:Microfilament Proteins / Q000737:chemistry / Q000494:pharmacology*; D010590:Phalloidine / Q000494:pharmacology; D011489:Protein Denaturation / Q000187:drug effects*; D017510:Protein Folding; D013696:Temperature; D013817:Thermography
D051339:Actin Depolymerizing Factors; D000199:Actins; D017607:Aluminum Compounds; D008840:Microfilament Proteins; D010590:Phalloidine; D005459:Fluorides; C032311:aluminum fluoride