Cytoskeleton III: Molecular Motors

Vocabulary flashcards covering key terms and concepts related to molecular motors, including myosins, kinesins, and dyneins, their structures, functions, and roles in cellular processes like muscle contraction, cytokinesis, and axonal transport.

Motor Proteins

Proteins that use energy from ATP hydrolysis to produce mechanical force, bind to the cytoskeleton, and move proteins or cargo.

Myosins

A family of motor proteins that move along actin filaments (AFs).

Kinesins

A family of motor proteins that move along microtubules (MTs) towards the plus (+) end.

Dyneins

A family of motor proteins that move along microtubules (MTs) towards the minus (-) end.

Conventional Myosins

Motor proteins like Myosin type II, involved in muscle contraction and cytokinesis.

Unconventional Myosins

Motor proteins such as Myosin type V, involved in organelle transport.

Myosin II Structure

Consists of heavy chains (with heads and tails) and light chains (essential and regulatory).

Myosin Head Region

The catalytic part of myosin that provides force and is conserved across different myosin types.

Myosin Tails

Portions of myosin that mediate dimerization with other myosins.

Myosin Light Chains

Components of Myosins that amplify conformational changes triggered during the myosin cycle.

Thick Filament

A structure formed by tail-tail interactions of Myosin II, with heads oriented in opposite directions, found within muscle sarcomeres.

Sarcomere

The fundamental contractile unit of striated muscle cells, containing organized thick (myosin) and thin (actin) filaments.

Tropomyosin

A protein that, in the absence of Ca2+, blocks the binding sites for myosin on actin filaments in muscle.

Troponin C

A component of the troponin complex that binds calcium ions, initiating muscle contraction.

Myosin II S1 Fragment

A cleaved portion of the myosin II molecule containing the catalytic head, used experimentally to demonstrate actin filament sliding.

Contractile Ring

A transient structure composed of Myosin II and actin filaments, crucial for cytokinesis during cell division.

Cytokinesis

The process of cell division that physically divides the cytoplasm of a parental cell into two daughter cells.

Myosin V

An unconventional myosin characterized by a long neck, known for its 'hand-over-hand' processive movement along actin filaments to transport cargo like organelles.

Processivity (Motor Proteins)

The ability of a motor protein to take multiple consecutive steps along its cytoskeletal track without detaching.

Axonal Transport

The movement of vesicles, organelles, and proteins along the axon of a neuron, mediated by motor proteins such as kinesins and dyneins.

AMP-PNP

A non-hydrolyzable analog of ATP used experimentally to demonstrate that motor proteins can bind to cytoskeletal tracks but cannot move without ATP hydrolysis.

Kinesin Structure

A motor protein with conserved head regions and diverse tail regions; its C-terminal domain typically attaches to cargo.

KIFC2

An atypical kinesin that moves toward the minus (-) end of microtubules, unlike most kinesins that move toward the plus (+) end.

Kinesin Linker Region

A region in kinesins that interacts with the catalytic core, causing a swinging arm motion during the kinesin cycle.

Cytoplasmic Dyneins

Dynein motors primarily involved in retrograde vesicular transport within the cell.

Axonemal Dyneins

Dynein motors responsible for the characteristic beating motion of cilia and flagella.

Dynactin Complex

An accessory protein complex that mediates the attachment of cytoplasmic dynein to its cargo and microtubules.