Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

PANEL 16–3 : Actin Filaments 905
ACTIN FILAMENTS
+
– – + +
–
+
–
–
+
–
+
–
+
–
+
formin
nucleates assembly and remains
associated with the growing
plus end
Arp2/3 complex
nucleates assembly
to form a web and remains
associated with the minus end
thymosin
binds subunits,
prevents assembly
– +
profilin
binds subunits,
speeds elongation
tropomodulin
actin subunits
prevents assembly and
disassembly at minus end
– +
actin filament
– +
cofilin
binds ADP-actin filaments,
accelerates disassembly
–
–
+
+
– +
tropomyosin
stabilizes filament
gelsolin
severs filaments and
binds to plus end
capping protein
prevents assembly and
disassembly at plus end
filament bundling, cross-linking, and attachment to membranes
fimbrin
plasma
membrane
α-actinin filamin spectrin
ERM
Some of the major accessory proteins of the actin cytoskeleton. Except for the myosin motor proteins, an example of each
major type is shown. Each of these is discussed in the text. However, most cells contain more than a hundred different
actin-binding proteins, and it is likely that there are important types of actin-associated proteins that are not yet recognized.