Dynein

Dynein

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Dynein is a motor protein (also called molecular motor or motor molecule) in cells which converts the chemical energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 contained in ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

 into the mechanical energy of movement. Dynein transports various cellular cargo by "walking" along cytoskeletal microtubule
Microtubule
Microtubules are a component of the cytoskeleton. These rope-like polymers of tubulin can grow as long as 25 micrometers and are highly dynamic. The outer diameter of microtubule is about 25 nm. Microtubules are important for maintaining cell structure, providing platforms for intracellular...

s towards the minus-end of the microtubule, which is usually oriented towards the cell center. Thus, they are called "minus-end directed motors," while kinesin
Kinesin
A kinesin is a protein belonging to a class of motor proteins found in eukaryotic cells. Kinesins move along microtubule filaments, and are powered by the hydrolysis of ATP . The active movement of kinesins supports several cellular functions including mitosis, meiosis and transport of cellular...

s, motor proteins that move toward the microtubules' plus end, are called plus-end directed motors.

Classification


Dyneins can be divided into two groups: cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

ic dyneins and axonemal
Axoneme
Numerous eukaryotic cells carry whip-like appendages whose inner core consists of a cytoskeletal structure called the axoneme....

 dyneins, which are also called ciliary or flagellar dyneins.
  • axonemal
    • heavy chain: DNAH1, DNAH2, DNAH3, DNAH5
      DNAH5
      Dynein heavy chain 5, axonemal is a protein that in humans is encoded by the DNAH5 gene.-External links:* -Further reading:...

      , DNAH6, DNAH7, DNAH8, DNAH9
      DNAH9
      Dynein heavy chain 9, axonemal is a protein that in humans is encoded by the DNAH9 gene.-Further reading:...

      , DNAH10, DNAH11
      DNAH11
      Dynein heavy chain 11, axonemal is a protein that in humans is encoded by the DNAH11 gene.-Function:This gene encodes a member of the dynein heavy chain family. It is a microtubule-dependent motor ATPase and has been reported to be involved in the movement of respiratory cilia...

      , DNAH12, DNAH13, DNAH14, DNAH17
    • intermediate chain: DNAI1
      DNAI1
      Dynein intermediate chain 1, axonemal is a protein that in humans is encoded by the DNAI1 gene.-External links:* -Further reading:...

      , DNAI2
      DNAI2
      Dynein intermediate chain 2, axonemal, also known as axonemal dynein intermediate chain 2, is a protein that in humans is encoded by the DNAI2 gene.- Function :...

    • light intermediate chain: DNALI1
    • light chain: DNAL1
      DNAL1
      Dynein light chain 1, axonemal is a protein that in humans is encoded by the DNAL1 gene.- Function :DNAL1 is a component of outer dynein arms, which contain the molecular motors for ATP-dependent cilia movement.- Clinical significance :...

      , DNAL4
      DNAL4
      Dynein light chain 4, axonemal is a protein that in humans is encoded by the DNAL4 gene.-Further reading:...


  • cytoplasmic
    • heavy chain: DYNC1H1
      DYNC1H1
      Cytoplasmic dynein 1 heavy chain 1 is a protein that in humans is encoded by the DYNC1H1 gene.-Interactions:DYNC1H1 has been shown to interact with PAFAH1B1 and CDC5L.-Further reading:...

      , DYNC2H1
      DYNC2H1
      Cytoplasmic dynein 2 heavy chain 1 is a protein that in humans is encoded by the DYNC2H1 gene.It is associated with Short rib-polydactyly syndrome type 3.It is also associated with Asphyxiating thoracic dysplasia.-Further reading:...

    • intermediate chain: DYNC1I1
      DYNC1I1
      Cytoplasmic dynein 1 intermediate chain 1 is a protein that in humans is encoded by the DYNC1I1 gene.In melanocytic cells DYNC1I1 gene expression may be regulated by MITF.-Further reading:...

      , DYNC1I2
      DYNC1I2
      Cytoplasmic dynein 1 intermediate chain 2 is a protein that in humans is encoded by the DYNC1I2 gene.-Further reading:...

    • light intermediate chain: DYNC1LI1
      DYNC1LI1
      Cytoplasmic dynein 1 light intermediate chain 1 is a protein that in humans is encoded by the DYNC1LI1 gene.-Further reading:...

      , DYNC1LI2
      DYNC1LI2
      Cytoplasmic dynein 1 light intermediate chain 2 is a protein that in humans is encoded by the DYNC1LI2 gene.-Further reading:...

      , DYNC2LI1
    • light chain: DYNLL1
      DYNLL1
      Dynein light chain 1, cytoplasmic is a protein that in humans is encoded by the DYNLL1 gene.-Interactions:DYNLL1 has been shown to interact with DLGAP1, MYO5A, DYNC1I1, BCL2L11, NRF1, IκBα, PAK1, DLG4 and TP53BP1.-Further reading:...

      , DYNLL2
      DYNLL2
      Dynein light chain 2, cytoplasmic is a protein that in humans is encoded by the DYNLL2 gene.-Interactions:DYNLL2 has been shown to interact with DLG4, DLGAP1, MYO5A and BMF.-Further reading:...

      , DYNLRB1
      DYNLRB1
      Dynein light chain roadblock-type 1 is a protein that in humans is encoded by the DYNLRB1 gene.-Further reading:...

      , DYNLRB2, DYNLT1
      DYNLT1
      Dynein light chain Tctex-type 1 is a protein that in humans is encoded by the DYNLT1 gene.-Further reading:...

      , DYNLT3
      DYNLT3
      Dynein, light chain, Tctex-type 3, also known as DYNLT3, is a protein which in humans is encoded by the DYNLT3 gene.- Function :DYNLT3 is a member of the dynein motor protein family. DYNLT3 binds to BUB3, a spindle checkpoint protein is present on kinetochores at prometaphase...


Function


Axonemal dynein causes sliding of microtubules in the axoneme
Axoneme
Numerous eukaryotic cells carry whip-like appendages whose inner core consists of a cytoskeletal structure called the axoneme....

s of cilia and flagella and is found only in cells that have those structures. Cytoplasmic dynein, found in all animal cells and possibly plant cells as well, performs functions necessary for cell survival such as organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....

 transport and centrosome
Centrosome
In cell biology, the centrosome is an organelle that serves as the main microtubule organizing center of the animal cell as well as a regulator of cell-cycle progression. It was discovered by Edouard Van Beneden in 1883...

 assembly.

Cytoplasmic dynein moves processively along the microtubule; that is, one or the other of its stalks is always attached to the microtubule so that the dynein can "walk" a considerable distance along a microtubule without detaching.

Cytoplasmic dynein probably helps to position the Golgi complex and other organelles in the cell. It also helps transport cargo needed for cell function such as vesicles
Vesicle (biology)
A vesicle is a bubble of liquid within another liquid, a supramolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sack that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes , or...

 made by the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...

, endosome
Endosome
In biology, an endosome is a membrane-bound compartment inside eukaryotic cells. It is a compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome. Molecules internalized from the plasma membrane can follow this pathway all the way to lysosomes for...

s, and lysosome
Lysosome
thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...

s (Karp, 2005). Dynein is also probably involved in the movement of chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

s and positioning the mitotic spindles for cell division. Dynein carries organelles and microtubule fragments along the axon
Axon
An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....

s of neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s in a process called axoplasmic transport
Axoplasmic transport
Axoplasmic transport, also called axonal transport, is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other cell parts to and from a neuron's cell body, through the cytoplasm of its axon...

 ).

Structure


Each molecule of the dynein motor is a complex protein assembly composed of many smaller polypeptide subunits. Cytoplasmic and axonemal dynein contain some of the same components, but they also contain some unique subunits.

Cytoplasmic dynein


Cytoplasmic dynein, which has a molecular mass of about 1.5 Megadaltons (MDa), contains approximately twelve polypeptide subunits: two identical "heavy chains," 520 kDa in mass, which contain the ATPase
ATPase
ATPases are a class of enzymes that catalyze the decomposition of adenosine triphosphate into adenosine diphosphate and a free phosphate ion. This dephosphorylation reaction releases energy, which the enzyme harnesses to drive other chemical reactions that would not otherwise occur...

 activity and are thus responsible for generating movement along the microtubule; two 74 kDa intermediate chains which are believed to anchor the dynein to its cargo; four 53-59 kDa intermediate chains and several light chains which are less understood.

The force-generating ATPase activity of each dynein heavy chain is located in its large doughnut-shaped "head", which is related to other AAA proteins
AAA proteins
AAA or AAA+ is an abbreviation for ATPases Associated with diverse cellular Activities. They share a common conserved module of approximately 230 amino acid residues...

, while two projections from the head connect it to other cytoplasmic structures. One projection, the coiled-coil stalk, binds to and "walks" along the surface of the microtubule via a repeated cycle of detachment and reattachment. The other projection, the extended tail (also called "stem"), binds to the intermediate and light chain subunits which attach the dynein to its cargo. The alternating activity of the paired heavy chains in the complete cytoplasmic dynein motor enables a single dynein molecule to transport its cargo by "walking" a considerable distance along a microtubule without becoming completely detached.

In eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s, cytoplasmic dynein must be activated by binding of dynactin
Dynactin
Dynactin or Dynein activator complex is a multi-subunit protein found in eukaryotic cells that aids in bidirectional intracellular transport by binding to dynein and Kinesin II and linking them to the organelle or vesicle to be transported....

, another multisubunit protein that is essential for mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

. Dynactin may regulate the activity of dynein, and possibly facilitates the attachment of dynein to its cargo.

Axonemal dynein


Axonemal dynein come in multiple forms that contain either one, two or three non-identical heavy chains (depending upon the organism and location in the cilium
Cilium
A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body....

). Each heavy chain has a globular motor domain with a doughnut-shaped structure believed to resemble that of other AAA proteins
AAA proteins
AAA or AAA+ is an abbreviation for ATPases Associated with diverse cellular Activities. They share a common conserved module of approximately 230 amino acid residues...

, a coiled coil "stalk" that binds to the microtubule, and an extended tail (or "stem") that attaches to a neighboring microtubule of the same axoneme
Axoneme
Numerous eukaryotic cells carry whip-like appendages whose inner core consists of a cytoskeletal structure called the axoneme....

. Each dynein molecule thus forms a cross-bridge between two adjacent microtubules of the ciliary axoneme. During the "power stroke", which causes movement, the AAA ATPase motor domain undergoes a conformational change that causes the microtubule-binding stalk to pivot relative to the cargo-binding tail with the result that one microtubule slides relative to the other (Karp, 2005). This sliding produces the bending movement needed for cilia to beat and propel the cell or other particles. Groups of dynein molecules responsible for movement in opposite directions are probably activated and inactivated in a coordinated fashion so that the cilia or flagella can move back and forth. The radial spoke
Radial spoke
The radial spoke is a multi-unit protein structure found in the axonemes of eukaryotic cilia and flagella. Although experiments have determined the importance of the radial spoke in the proper function of these organelles, its structure and mode of action remain poorly understood.- Cellular...

has been proposed as the (or one of the) structures that synchronizes this movement.

History


The protein responsible for movement of cilia and flagella was first discovered and named dynein in 1963 (Karp, 2005). 20 years later, cytoplasmic dynein, which had been suspected to exist since the discovery of flagellar dynein, was isolated and identified (Karp, 2005).

External links