What is the Difference Between Cytoplasmic and Axonemal Dynein

The key difference between cytoplasmic and axonemal dynein is that cytoplasmic dynein is found in all animal cells and plant cells, while axonemal dynein is only found in cells that have structures like cilia and flagella.

Dynein is a motor protein that moves along microtubules in the cells. It normally converts the chemical energy stored in ATP to mechanical work. Dynein transports various cellular cargos, provides forces and displacements important in cell divisions such as mitosis, and drives the beat of structures like eukaryotic cilia and flagella. There are two types of dynein proteins: cytoplasmic and axonemal dynein.

CONTENTS

1. Overview and Key Difference
2. What is Cytoplasmic Dynein
3. What is Axonemal Dynein
4. Similarities – Cytoplasmic and Axonemal Dynein
5. Cytoplasmic vs Axonemal Dynein in Tabular Form
6. Summary – Cytoplasmic vs Axonemal Dynein

What is Cytoplasmic Dynein?

Cytoplasmic dynein is a type of dynein protein found in all animal cells and plant cells. It is the major microtubule-based motor protein for cargo transport toward microtubule minus ends. Cytoplasmic dynein is a large protein complex that contains twelve subunits. The molecular weight of this protein complex is around 1.5 MDa. The largest subunits are the heavy chains (DYNCIH1, DYNC2H1), and they have distinct head and tail domains. The head contains the motor with microtubule binding and ATP hydrolysis domains that generate the movement along microtubules. The other ten subunits are two intermediate chains (DYNC1I1, DYNC1I2), two light intermediate chains (DYNC1LI, DYNC1L2), and several light chains (DYNLL1, DYNLL2, DYNLRB1, DYNLRB2, DYNLT1, and DYNLT3). These ten subunits bind directly or indirectly to the tail of the heavy chain (head) and comprise the cargo binding domains.

Moreover, cytoplasmic dynein performs functions necessary for cell survival, such as organelle transport and centrosome assembly. Furthermore, cytoplasmic dynein helps to position the Golgi complex and other organelles in the cell. In addition, it helps transport cargo that is needed for cell function, such as vesicles made by the endoplasmic reticulum, endosomes, and lysosomes.

What is Axonemal Dynein?

Axonemal dynein is a type of dynein motor protein only found in cells that have structures like cilia and flagella. Axonemal dynein was the first dynein to be discovered in 1963. Structurally, Axonemal dynein has 8 subunits. It consists of three non-identical heavy chains (DNAH1, DNAH2, and DNAH3). Each heavy chain has a globular motor domain with a doughnut-shaped structure, a coiled-coil “stalk” that binds to the microtubule, and an extended tail that attaches to the neighboring microtubule of the same axoneme. Other subunits include intermediate chain (DNAI1 and DNAI2), light intermediate chain (DNALI1), and light chain (DNAL1 and DNAL4).

Moreover, dynein causes the sliding of microtubules in the axonemes of cilia and flagella. It is only found in cells that have those structures. Furthermore, the regulation of axonemal dynein activity is very critical for flagella beat frequently and the wave form of cilia. This regulation is made by phosphorylation, redox reaction, and calcium.

What are the Similarities Between Cytoplasmic and Axonemal Dynein?

• Cytoplasmic and axonemal dynein are two types of dynein proteins.
• Both are motor proteins that move along microtubules in the cells.
• Both are made up of amino acids.
• Structurally, both dynein have subunits.
• They perform a very important function in the cell.

What is the Difference Between Cytoplasmic and Axonemal Dynein?

Cytoplasmic dynein is found in all animal cells and possibly in plants cells as well, while axonemal dynein is only found in cells that have structures like cilia and flagella. Thus, this is the key difference between cytoplasmic and axonemal dynein.

The below infographic presents the differences between cytoplasmic and axonemal dynein in tabular form for side by side comparison.

Summary – Cytoplasmic vs Axonemal Dynein

Cytoplasmic and axonemal dynein are two types of dynein proteins. Cytoplasmic dynein is found in all animal cells and possibly in plant cells as well, while axonemal dynein is only found in cells that have structures like cilia and flagella. So, this is the summary of the difference between cytoplasmic and axonemal dynein.

Reference:

1. “Cytoplasmic Dynein.” An Overview | ScienceDirect Topics.
2. “Axonemal Dynein.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “DyneinHeavyChainOnMT” By TheTrappist – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Eukaryotic flagellum” By en:User:Smartse – File:Axoneme.JPG and Figure 19.28 on page 819 of “Molecular Cell Biology, 4th edition, Lodish and Berk”; ISBN 0-7167-3706-X (CC BY-SA 3.0) via Commons Wikimedia