Lecture 3 Flashcards
How many forms of actin did we study and what were their names?
G-Actin (Globular actin) and F-Actin (Filament ActIn)
What is bound in the G-Actin binding cleft?
Mg2+ and an ATP molecule that can be hydrolysed
What causes polymerisation of the G-Actin monomers to occur?
The polar nature of G-Actin molecules causes them to be attracted to each other, and above a critical concentration this results in the formation of a nucleus from which the filament will grow in both directions
What are the three phases of polymerization of actin filaments?
Nucleation, elongation and steady state
What is treadmilling and how does it occur?
As the actin filament grows preferentially at the +ve end, this means that at a critical concentration Actin monomers will dissociate from the -ve end and then go and bind to the +ve end resulting in movement of the actin filament
What does Profilin do with regards to actin filaments?
Profilin exchanges ADP with ATP on the actin monomer which drives treadmilling as ATP G actin binds from the +ve end
What does Gelsolin/Cofilin do with regards to the actin filament?
This protein caps the growing +ve end and allows for depolymerisation to occur at the -ve end of the microfilament
What does Srp 2/3 do with regards to the actin filament?
Arp 2/3 promotes branching of the actin filament
What are the 4 steps in cellular movement?
Extension of the lamellipodia
Adhesion of the Lamellipodia
Flow of Cytosol
Retraction of the rear of the cell
What are the three classes of myosin and what do they act as?
Myosin I which acts on the cell membrane helping with things such as endocytosis and cell recognition
Myosin II which forms the thick filaments in sacromeres
Myosin 5 which forms a dimer used to transport cargo along microfilaments within the cell
What are the steps in the process of muscle contraction in skeletal muscle?
Ca2+ is released by a neuron, this binds to troponin which causes a confromation change which moves tropomyosin which uncovers the myosin binding site on the actin filament which a,lows muscle contraction to occur
What are the steps in muscle contraction in smooth muscle?
Ca2+ is released by a nerve impulse, This activates myosin light chain kinase, this phosphorylates the myosin head resulting in it being able to undergo its mechanochemical cycle
