Dyneins hold crucial functions in biological movements, no matter within the cell or across cell. A research team has been looking at their presence and functions in Dictyostelium discoideum, a type of amoeba. These cytoskeletal motor proteins are known to 'walk' along microtubules in cells to carryout cell functions such as cell division, migration, end-directed intercellular transport of vesicles and organelles; axonemal dyneins are even specialised in ciliary and flagellar beating.
 |
| 3VKH - wild type Dictyostelium discoideum cytoplasmic dynein |
Overview
Dyneins are microtubule-based motor complexes which have heavy chains of over 500 kDa. Although similar in nature with cytoskeletal motor proteins which are relatives of G proteins by evolution, dyneins are instead closer related to AAA+ superfamily of mechanochemical enzymes, such as ring type ATPases. Hence, dynein possesses the conserved ATPase units, of 6 AAA+ modules arranged as a ring structure, all in one polypeptide. Not until recent years, little has been understood properly about dyneins in terms of molecular mechanism, as opposed to common AAA+ or motor proteins, due to the lack of structural information acquired from high resolution sources - crystal structures of cytoplasmic dynein motor domains at 4.5-6 Å resolution was only enough for showing secondary protein structures. Thanks to a protein macromolecular science research team in University of Osaka and Tokyo, the crystal structure of cytoplasmic dynein in Dictyostelium at 2.8 Å, with 90% of amino acids traced, has been examined and studied finally. This enables us to understand the mechanism of cytoplasmic dyneins’ famous walks on microtubules, through looking at how the motor protein generates force and moves, based upon its atomic structure.
No comments:
Post a Comment