Final answer:
G-actin monomers polymerize to form F-actin, which participates in various cellular functions including muscle contraction and cell motility. ATP binding and hydrolysis drive the dynamic behavior of actin filaments, characterized by differing polymerization rates at the '+end' and '-end.'
Step-by-step explanation:
Globular actin (G-actin) monomers are vital for the construction of microfilaments and cell motility in eukaryotic cells. The structure of Actin monomers consists of a single polypeptide chain that can bind ATP and polymerize to form two intertwined helical strands known as F-actin. These polymers are chiral and polar, meaning that their two ends, designated as '+end' and '-end,' are not equivalent, which affects their dynamic behavior in cells, including polymerization and depolymerization rates.
The non-equilibrium process of actin polymerization is driven by ATP binding to G-actin monomers; ATP hydrolysis then decreases the stability of the chain, leading to dynamic behavior such as treadmilling, where actin monomers can continuously add to the '+end' and dissociate from the '-end.' This process allows actin to participate in various cellular mechanisms including muscle contraction, cell shape changes, and movement.
High-resolution electron micrographs have shown that G-actin monomers decorate the sides of F-actin, identifying them as actin by the characteristic arrowhead pattern when decorated with myosin S1 fragments. This demonstrates the interaction between actin and myosin, crucial in muscle contraction and cell motility in non-muscle cells.