Chapter 14 - ABPs and MAPs

binds subunits, prevents assembly

Thymosin β4

binds subunits, speeds elongation

Profilin

nucleation assembly and remains associated with the growing plus end

Formins

nucleates assembly to form a web and remains associated with the minus end

Arp 2/3 Complex

_______ caps the (+) end of actin filaments and prevents assembly and disassembly

CapZ

______ caps the (–) end of actin filaments

Tropomodulin

Stabilizes actin filaments

Tropomyosin

binds ADP-actin filaments and accelerates disassembly

Cofilin

Gelsolin activity is activated by an increase in _______ concentration

Calcium

Crosslinking proteins with flexible spacers like _______ and _______ organize filaments into gel-like networks

Filamin; Spectrin

Proteins like _______ and _______ with short spacers promote tight filament bundles

Fimbrin; Fascin

_______ can crosslink filaments into parallel and anti-parallel bundles involved in contraction

α-actinin

ERM proteins (e.g., _______) link F-actin to the membrane via peripheral proteins

Ezrin

_______ links cortical actin to muscle membranes via the Dystroglycan complex

Dystrophin

Mutations in spectrin, ankyrin, or band 4.1 can result in _______ _______ anemias.

Hereditary spherocytic

Duchenne Muscular Dystrophy is caused by loss of function in the _______ protein

Dystrophin

_______ binds and sequesters tubulin oligomers to promote catastrophe

Stathmin

The primary microtubule nucleator at the centrosome is _______

γ-TURC

+TIPs like _______ and _______ regulate dynamics and bind MT (+) ends

EB1, CLIP-170

_______ severs MTs and promotes depolymerization at (–) ends

Katanin

_______ promotes MT depolymerization at the (+) end by inducing protofilament curling

Kinesin-13

Polymer-binding MAPs have a _______ domain that binds MTs and a _______ domain that interacts with other structures

Microtubule-binding, Projection

MAPs like _______ and _______ are crucial for organizing MTs in neurons

MAP2, Tau

Tau has a shorter projection domain than MAP2, leading to _______ spacing between microtubules

Tighter

In Alzheimer’s disease, Tau is often found in hyperphosphorylated and aggregated form called ____________ ______

Neurofibrillary tangles

Tau dysfunction leads to loss of microtubule _______ and reduced _______ transport

Stability, Axonal