Dynein Motor Protein Literature Review

Cell Biology BI309 Mini-Review 1 Title: Dynein Motor Proteins

In order for eukaryotic cells to be motile they use motor proteins that are propelled by ATP. There are three classes of motor proteins; myosin, kinesin and dynein. Dynein is the motor protein to be discussed in detail for this review. Dynein is a large and complex motor protein found in microtubules of cilia and flagella that causes movement due to the conversion of Adenosine Triphosphate(ATP) which is a form of chemical energy to mechanical energy i.e. movement. Due to the large mass of the dynein protein, it has been quite a challenge to explain the function and mechanism of dynein. Through experimentation developments have been made in recent years into comprehending how dynein

In particular there are many cilia and flagella present in the lung. Axonemes make up the cilia and flagellum. They are present in 9 sets of doublets. As shown in Figure 1.1 (a). Axonemal dynein proteins are attached to doublets on the inner and outer arms. Although axonemal dyneins are present in the axoneme, they are not fundamental in the formation of axonemes. Inner arms have six of one heavy chain dynein with one head and one of a one heavy chain dynein with two heads. This is a pattern that repeats itself every 96nm. On the outer arms the dyneins are the same with three different heavy chains. The dynein also has a flexible stem, globular head as well as a thin string with the ATP binding site. Axonemal dynein proteins cause microtubules to move and thus the cilia and flagella move by a beating process. Cilia and flagella have very similar structure so it is very difficult to distinguish them from each other at times. However we can distinguish between them from their movement. Flagella move in a wave like motion where as cilia move in a sling shot motion. When multiple cilia move at the same time in the same direction. Large cargoes can be moved quickly. Cilia move or "beat" one hundred times per second. (Pollard et al,

The cytoplasmic dynein goes in the direction of the minus terminus of the microtubule. While no molecule is bound to the AAA1 ATP binding site, the dynein is securely bound to the microtubule. When ATP binds to the AA1 ATP binding site, the dynein quickly unbinds the tight bond between itself and the microtubule. When ATP is bound to the site. ADP is released as well as inorganic phosphate. The motor domain then is involved with a new binding site on the microtubule and catalyses the production of inorganic phosphate. This causes the linker to go back to its straight form of structure. (Roberts et al.