M Type Kinesins
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
| This article is orphaned as few or no other articles link to it. Please help introduce links in articles on related topics. |
 |
This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. |
M Type Kinesins (KIF-M) are a subfamily of the molecular motor proteins known as kinesins. Simply stated, their task is to transport materials or cargo around the cell while traversing along microtubule polymer tracks with the help of ATP-hydrolysis-created energy. They are easily identified by their three typical structural components including a highly conserved structural domain, catalytic core, and microtubule binding sites. Composed of only one class, KIF2, the KIF-M family is less understood than KIF-Ns (with their catalytic core at the N-terminus) or KIF-Cs (with their catalytic core at the C-terminus). They were initially named KIF-M because of the unique location of their catalytic core in the middle of the polypeptide between the N-terminal globular domain and the C-terminal stalk but they are truly special due to their versatile nature. They are capable of traveling to both the minus and plus ends of microtubules whereas most motors are unidirectional. Thus they can catalytically depolymerize a microtubule from both ends making it a very efficient process.
The exact mechanism of KIF-M activated microtubule depolymerization remains unclear, however, recent biochemical and structural studies revealed some more detailed class specific features enabling researchers to formulate the following model. (Refer to Figure 6 in referenced Ogawa article for illustrated description.) KIF-M first contacts the side wall of a microtubule. This is not a stable interaction because the convex surface of the catalytic core does not fit to the flat surface of the straight microtubule protofilament. Steric hindrance between the KIF-M neck and adjacent protofilament further inhibits full contact between KIF-M and the microtubule and only facilitates one-dimensional diffusion along the microtubule. At this time, KIF-M's nucleotide binding pocket is trapped in an open state so that the structure is not hydrolyzing ATP. Once the motor reaches the end of the microtubule, the protofilament spontaneously curves itself allowing KIF-M to make full contact with the tubulin subunit. More KIF-M molecules collectively bind to the curved region supporting the theory that they do not actively peel away the microtubule but they wait patiently for it to adopt this curved conformation. They stabilize the curved conformation by binding to the end of the microtubule and then catalyze depolymerization.
References
Ogawa, T., Nitta, R., Okada, Y., and N. Hirokawa (2004) Cell 116: 591-602. A Common Mechanism for Microtubule Destabilizers—M Type Kinesins Stabilize Curling of the Protofilament Using the Class-Specific Neck and Loops
External Links
For Video Illustrations: [1]
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
