#motor protein

Elegans -ll

Which motor protein is responsible for P-granule migration?

P-granules, ribonucleoprotein assemblies marking germline, segregate to posterior blastomere P1 during first division and subsequently to germline precursors P2-P4. Their posterior migration along cell cortex before division requires microtubule motor dynein transporting granule components along cortical microtubules toward centrosome at posterior pole. PAR-1 dependent microtubule organization creates flow. Mutants in dynein heavy chain dhc-1 or its regulator dynactin cause equal distribution of P-granules to both AB and P1, losing germline restriction. Myosin II and kinesin contribute to cort

Ref: Updike & Strome 2010; Gilbert Chapter 4: Dynein motor responsible for P-granule migration in early embryo.

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Cytoskeleton

Which component of dynein is primarily responsible for generating movement?

Generation of force in dynein occurs in motor domain comprising six AAA+ modules organized in a closed ring with large linker arching over it. AAA1 through AAA4 can bind nucleotide, but only AAA1 and AAA3 hydrolyze productively to drive movement. In ATP-bound state AAA1-AAA2 closure pulls AAA2 away from AAA3, propagating conformational change through AAA4-AAA6 to stalk coiled-coil, shifting registry and lowering affinity for microtubule. Subsequent phosphate release closes ring further, driving linker domain rotation of approximately eight nanometers from straight to bent conformation docked a

Ref: Carter Nature 2011; AAA+ ring AAA1 hydrolyzes ATP driving linker swing, motor core force.

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Cytoskeleton

Which motor protein moves cilia and flagella?

Cilia and flagella motility requires active sliding filament machine within conserved axoneme evolutionary ancient. Structure nine outer doublet microtubules surrounding central pair retains dynein motors as exclusive driver of beating: outer dynein arms contain two or three heavy chains per arm inner arms more heterogeneous but also axonemal dynein isoforms both anchored to A tubule via docking complex and reaching to B tubule of neighboring doublet executing ATP hydrolysis cycle. Power stroke toward minus end attempts to slide doublets relative each other but nexin dynein regulatory complex

Ref: King, J Cell Sci 2012 – Dynein motor protein moves cilia and flagella beating machinery.

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Cytoskeleton

Which motor protein powers ciliary and flagellar movement?

Motile cilia and flagella beating powered exclusively by axonemal dynein distinct isoforms from cytoplasmic dynein-1 adapted for high duty cycle sliding. Outer and inner dynein arms attached every 24 and 96 nm along A tubule heavy chains contain AAA ring and microtubule binding stalk pointing toward adjacent B tubule executing ATP hydrolysis cycle. Cycle drives linker bending delivering power stroke causing interdoublet sliding about 5 microns per second in disintegrated axoneme. In intact cilia doublets anchored at basal body and crosslinked by nexin dynein regulatory complex forces converted

Ref: Viswanadha et al., Biosci Rep 2017 – Dynein powers ciliary and flagellar movement via axonemal arms.

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Cytoskeleton

Kinesin-13 differs from other kinesins because it:

Kinesin superfamily generally couples ATP hydrolysis to processive stepping for cargo transport using hand over hand mechanism but kinesin-13 family including mitotic centromere associated kinesin MCAK KIF2C and KIF2A exhibits depolymerase activity instead of transport. These kinesins possess central motor domain flanked by N and C termini diffuse along microtubule lattice without directional ATP dependent stepping and concentrate at ends via one dimensional diffusion to both tips. At tip they stabilize curved protofilament conformation accelerating removal of tubulin subunits and inducing cat

Ref: Walczak et al., Annu Rev Cell Dev Biol – Kinesin-13 depolymerase activity mechanism classification.

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Cytoskeleton

What is the primary function of dynein in cellular transport?

Cellular cargo movement includes vesicular trafficking but cilia and flagella beating demands distinct high power motors specialized for sliding instead of cargo carrying. Axonemal dynein evolved from cytoplasmic dynein forms large arrays of outer and inner dynein arms repeating every 96 nm along A tubule of axonemal doublet in nine fold symmetric axoneme. Each arm hydrolyzes ATP in AAA1 to AAA4 rings transmitting conformational change through stalk causing sliding of adjacent B tubule toward base at velocities up to 5 microns per second. Because axoneme constrained by radial spokes linking do

Ref: Ishikawa, Curr Biol – Dynein generates force for cilia flagella movement via axonemal arms.

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Cytoskeleton

Which motor protein moves cargo towards the (+) end of microtubules?

Long distance intracellular transport along microtubules employs directional motors whose motor domains read polarity via asymmetric binding and neck linker orientation. Majority of kinesin superfamily members possess N terminal motor domains that exhibit plus end directed motility via neck linker docking mechanism: ATP binding induces neck linker zippering toward plus end swinging trailing head forward 8 nm. Kinesin-1 KIF5B exemplifies conventional plus motor ferrying mitochondria synaptic vesicle precursors lysosomes and mRNP anterogradely toward cell periphery or axon terminals at about 1 m

Ref: Vale, Cell 2003 – Kinesin family plus end motility; Alberts Chapter 16 Kinesin-1 transport role.

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Cytoskeleton

Actin filaments interact with which motor protein for intracellular transport?

Two distinct superfamilies of cytoskeletal motors evolved to walk along filaments using ATP hydrolysis. Myosin motors share N terminal head motor domain containing actin binding interface including helix turn helix, cardiomyopathy loop, P loop ATPase, Switch I II for gamma phosphate sensing and lever arm with IQ motifs binding calmodulin light chains. Upon interaction with F actin 7 nanometer helical filament, head undergoes conformational cycle releasing phosphate driving swing of lever arm producing force along filament. Diverse isoforms specialize: myosin II non processive forming bipolar f

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 16: Myosin Motors and Actin Filaments.

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