A 42kD actin filament severing and capping
protein from Physarum polycephalum which shares many properties with severin
gelsolin but has in addition some rather surprising exclusive features. Actin in
complex with fragmin has been found to be phosphorylated on threonines 202 and
203. These residues are involved in
contacts with DNAse 1 and actin itself so it is likely that this would result in
an inhibition of polymerization, also it has been found that the kinase binds
very tightly to the fragmin actin complex. Recently another fragmin like protein
has been isolated from Physarum which
has a molecular weight of 60kD.
here for a
diagram of the domain structure of the Gelsolin/Villin
C. and J.
"The F-actin capping proteins of Physarum
polycephalum: cap42(a) is very similar, if not identical, to fragmin and is
structurally and functionally very homologous to gelsolin; cap42(b) is Physarum