Open AccessThe influence of substoichiometric concentrations of myosin subfragment 1 on the state of aggregation of actin under depolymerizing conditions
Author(s) -
GRAZI Enrico,
MAGRI Ermes,
RIZZIERI Luciana
Publication year - 1989
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1989.tb14827.x
Subject(s) - depolymerization , myosin , actin , chemistry , monomer , biophysics , myosin head , actina , protein filament , myosin light chain kinase , biochemistry , cytoskeleton , polymer , biology , polymer chemistry , organic chemistry , cell
In 3 mM KCl, 2 mM Tris/HCl pH 7.5, 22°C, 0.38 μ myosin subfragment 1 delays the depolymerization of F‐actin (7.2 μ measured as monomer). The depolymerization proceeds rapidly for a few minutes and then slows down suddenly when the ratio between the monomers in the actin filaments and myosin subfragment 1 reaches the value of 11. At this time myosin subfragment 1 is substantially all bound to the actin polymers which form an irregular and discontinuous network of filaments running in doublets and in triplets, perhaps cross‐linked by myosin subfragment 1. Depolymerization proceeds then for several hours, apparently ending up with the formation of the 1:1 actin‐S1 heteropolymer. The ratio between the monomers in the actin filaments and myosin subfragment 1 at the end of the rapid depolymerization proceeds is different for different protein preparations and may be as low as 5.5. In 2 mM Tris/HCl pH 7.5, 25°C, 1 μ myosin subfragment 1 is able to induce the formation of undecorated actin filaments from 12 μ ATP–G‐actin. These filaments probably originate by redistribution of myosin subfragment 1 between the newly formed 1/1 actin‐S1 heteropolymer and G‐actin in the medium, a process which allows the transient formation of undecorated actin filaments.