actin Flashcards
what are the main types of actin accessory proteins?
polymerizing nucleating bundling capping severing gelating motor proteins
what are polymerizing proteins? example
they add actin monomers to the filament. Profilin adds to the plus end
what are nucleating protein? example
they allow the cell to control the time and place of de novo actin filament assemble. Arp2/3 and Formin nucleate actin filaments in vivo
What do Profilin and Formin do and how?
together they add actin monomers to the plus end of the filament. Formin proteins have long whiskers that bind profilin-actin complexes which adds actin to filament end. Formin only nucleates unbranched filaments
what is the difference between Formin and Arp2/3?
Formin nucleates unbranched filaments
Arp2/3 nucleates branched filament networks. always creates a 70 degree angle in branches
what did Arps arise from?
gene duplication and divergence of actin. Arps are 45% identical to actin in amino acid structure
how do Arps work? describe steps in process
Arp is activated by a signaling protein and will come together with other proteins to form a complex. The complex attaches to the side of a filament and adds actin monomers in branches at 70 degree angle to the original filament
How can bacteria exploit actin polymerization?
the assembly of actin on a bacterias back surface propels the bacterial forward, helping them invade neighboring cells and maintain infection. Listeria monocytogenes is an example of bacteria doing this
what are capping proteins?
they stabilize actin filament length and inhibit further elongation. They can bind to either the plus or minus end
what are severing and depolymerizing proteins? example
they accelerate the disassembly of actin filaments by severing and depolymerizing. Cofilin
how does Cofilin work?
Cofilin binds to actin filaments and increases the apparent twist, weakening non covalent bonds and destabilizing filament.
what are bundling proteins?
they organize actin filaments into bundles. some pack them tightly and some loose.
what are cross linking proteins? example
they connect actin filaments into lattice like structures important for cell crawling (filopodia and pseudopodia). Filamin
what diseases can be caused from defective filamin?
Periventricular Heteropia is caused by a mutation in filamin A gene. This causes failure of neurons to migrate during development and patients often have epilepsy.
what causes Duchenne Muscular Dystrophy?
mutation of the protein Dystrophin, a cross linking protein