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Cell surface (cortical) actin remodeling is a cyclic (9-step) process where each step is directly responsive to a cell signaling mechanism. Over the course of the cycle, actin begins as a monomer, elongates into a polymer with the help of attached actin-binding-proteins, and disassembles back into a monomer so the remodeling cycle may commence again.
Many actin-related molecules create a free barbed end for polymerization by uncapping or severing pre-existing filaments and using these as actin nucleation cores. However, the Arp2/3 complex stimulates actin polymerization by creating a new nucleation core. Actin nucleation is an initial step in the formation of an actin filament.
Actin plays a role in the formation of new spines as well as stabilizing spine volume increase. [1] The changes that actin brings about lead to the formation of new synapses as well as increased cell communication. Actin remodeling consists of the dynamic changes in actin polymerization that underlie the morphological changes at the neural synapse.
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils.It is found in essentially all eukaryotic cells, where it may be present at a concentration of over 100 μM; its mass is roughly 42 kDa, with a diameter of 4 to 7 nm.
(Single white dots represent monomers and black chains represent oligomers and polymers) [1] Comparison of molecular weight vs conversion plot between step-growth and living chain-growth polymerization. In polymer chemistry, step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional ...
In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical, cation, or anion. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers.
The unfavorable kinetics of actin oligomer production prevent spontaneous actin polymerization. [2] Once an actin nucleus has been created, the connection of the monomers happens swiftly, with the plus end developing considerably more quickly than the minus end. [2] Actin's ATPase activity sharply rises after insertion into the filament. [2]
Microfilament Polymerization. Microfilament polymerization is divided into three steps. The nucleation step is the first step, and it is the rate limiting and slowest step of the process. Elongation is the next step in this process, and it is the rapid addition of actin monomers at both the plus and minus end of the microfilament.