Forms two types of fibre: microfilaments (part of the cytoskeleton) and parts of muscle fibres
As a monomer it is called Globular (G)-actin, and as a fibre it is called F-actin. F-actin (actin fibres) are polymers of G-actin
Actin polymerisation is an active process that uses ATP as a source of energy. Actin hydrolyses ATP into ADP - it is an ATPase. The actin cytoskeleton is highly dynamic
Binds F-actin in the middle of a fibre and can act as a nucleation site for a new fibre, causing actin branching with a characteristic branch angle of 70 degrees
If the rate of polymerisation and depolymerisation are equal the fibre stays the same length but moves in the direction of the barbed end. Depends on the concentration of actin monomers (G-actin) and the presence of actin binding proteins
The next most important part of the cytoskeleton. Like actin they have a structural role and generate force, but are also very important for transport of substances around the cell
A central organelle containing a pair of centrioles (also made of tubulin) that contain a special kind of tubulin called g-tubulin. The MTOC is usually located near the nucleus
Drugs that interfere with tubulin and microtubules are often used in chemotherapy to block cell division (mitosis). An example is the drug Taxol, purified from the Pacific Yew tree which blocks microtubule disassembly
A family of around 10 structurally related proteins which all serve a similar structural role but are not active - they do not contain ATP or GTP binding sites and do not undergo tread-milling. They include vimentin, spectrin, keratin and lamins
Proteins that move along actin or tubulin fibres. Their role is to generate force to either move cargo (e.g. a membranous vesicle) along the fibre or to move the fibre itself. Some common types are Myosin (which move along actin fibres) and Dynein and Kinesin which move along microtubules