Alpha-actinin increases actin filament end concentration by inhibiting annealing.
The usual rate of actin polymerization is increased if one starts from actin nuclei. We have noticed that, using alpha-actinin crosslinked actin nuclei, the initial net elongation rate is further enhanced. Also initial net depolymerization rates of alpha-actinin crosslinked F-actin samples are higher than those of controls. These results should imply that alpha-actinin increases the filament end concentration of actin samples. The experiments with barbed and blocking substances (cytochalasin D and gelsolin-actin complex) confirmed such an increase. We have shown that: (1) alpha-actinin does not significantly influence actin polymerization over all; (2) alpha-actinin inhibits the recovery of the filament size in F-actin samples after sonication; and (3) the influence of alpha-actinin on actin filament end concentration is counteracted by tropomyosin. Therefore, we suggest that, upon filament shearing, alpha-actinin crosslinking inhibits the annealing of short actin polymers into longer filaments.
University of Milan, Department of Biology, Italy.
R
R
Colombo
I
I
DalleDonne
A
A
Milzani
D000185:Actinin / Q000378:metabolism*; D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D018260:Gelsolin; D008840:Microfilament Proteins / Q000494:pharmacology; D013010:Sonication; D014335:Tropomyosin / Q000494:pharmacology
D000199:Actins; D002135:Calcium-Binding Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; D014335:Tropomyosin; D000185:Actinin; D015638:Cytochalasin D