BIOL 2021 Lecture Notes - Lecture 14: Cell Cortex, Formins, Profilin
13 May 2018
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• Actin nucleation,
• Fig 16-16B actin filament nucleation by ARP
o ARP = actin related proteins.
o ARP complex nucleates actin filaments from minus end.
o Signals cause activation of proteins that activate ARP.
o Mostly found in cell cortex = outer region beneath PM.
o In the absence of an activating factor, Arps are held by their accessory
proteins in an orientation that prevents them from nucleating a new actin
filament. When an activating factor (indicated by the blue triangle) binds
the complex, Arps are brought together into a new configuration.
• Fig 16-16C actin webs
o ARPs can bind to side of actin filaments.
o ARP tends to form actin webs, branching.
• Fig 16-17 formins
o Formins = nucleate actin filaments.
o Make straight unbranched actin bundles.
o Stay bound to plus end and encourage actin monomers to bind and
extend the filament.
o Also found in cell cortex.
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