The Molecules of Movement Flashcards
What are the three types of molecular motor?
Linear
Oscillatory
Rotatory
What is a molecular motor?
A protein assembly that converts chemical energy into mechanical energy.
Give examples of protein rails that are used by linear motors.
Myosin uses actin. Kinesin and dynein use microtubules. Helicases and topoisomerases use DNA and RNA.
Where are oscillatory motors found?
In cilia - they form cross-linked microtubule bundles called axonemes and are powered by dynein
What are microtubules made up of?
Alpha and beta tubulin
The microtubules are polarised. Which end is positive and which is negative?
Negative nucleus
Positive periphery
What are the two motors that travel down these microtubules and which directions do they move in?
Kinesin - towards the positive
Dynein - towards the negative
Give some features of F-actin.
It is inextensible, dual-stranded helix, and it is polar
In which direction do myosin move along actin?
Move towards the positive end
What does myosin consist of?
Two heavy chains and two light chains
What type of myosin is found in a) muscle and b) brain?
Muscle = Myosin II Brain = Myosin V
What is the difference between myosin in muscle and myosin in the brain?
Myosin in the brain is processive - this means that the myosin is always in contact with the actin whereas in muscle the myosin can detach from the actin.
What is the structure of myosin filaments?
Myosin filaments form anti-parallel dimers - so there is a region in the middle that doesn’t have any myosin heads and hence cannot form cross-bridges
Describe the structure of kinesin.
Kinesin consists of two amino acid side chains.
The ends of the side chains have globular ATP binding heads
The heads interact with the microtubules and the tails hold the cargo
Describe why kinesin is described as processive and myosin is not processive.
.
The kinesin is always in contact with the microtubule whereas the myosin an detach from the actin
