aktiinimonomerejä

Aktiinimonomerejä, also known as G-actin, are globular protein subunits that polymerize to form filamentous actin, or F-actin. These monomers are essential components of the cytoskeleton in eukaryotic cells, playing crucial roles in cell shape, movement, and intracellular transport. Each actin monomer is approximately 42 kDa in size and possesses a binding site for ATP.

The polymerization process of G-actin into F-actin is a dynamic and reversible event. In the presence of appropriate ionic conditions and ATP, G-actin monomers bind to each other end-to-end, forming a helical filament. This polymerization is often described as a treadmilling process, where monomers are added to one end of the filament and dissociate from the other, allowing for continuous remodeling of the actin cytoskeleton.

The binding of ATP to G-actin is critical for polymerization. Once incorporated into the filament, ATP is hydrolyzed to ADP, which can then be replaced by another ATP-bound G-actin monomer. This hydrolysis influences the stability of the filament and the rate of polymerization and depolymerization.

Actin filaments are highly versatile and interact with a variety of actin-binding proteins (ABPs) that regulate their assembly, disassembly, and function. These interactions allow cells to generate forces, form structures like microvilli and lamellipodia, and facilitate processes such as cell division and muscle contraction. The precise regulation of actin monomer dynamics is therefore fundamental to cellular life.