An actin-binding protein called cofilin binds preferentially to ADP-containing actin filaments rather than ATP-containing actin filaments. Based on this preference, which is true? Question 7 options: Cofilin binds to the plus ends of treadmilling actin filaments. Cofilin competes with profilin for binding to actin. Cofilin binds to older actin filaments. Cofilin binds to the plus ends of actin filaments.

Cofilin binds to older actin filaments

Explanation:

Microfilaments (also called actin filaments) are a class of protein filament common to all eukaryotic cells, which consist of two strands of subunits of the protein actin. Microfilaments form part of the cell's cytoskeleton and interact with the protein myosin in order to allow the movement of the cell. Within the cell, actin may show two different forms: monomeric G-actin and polymeric F-actin filaments. Microfilaments provide shape to the cell because these filaments can depolymerize (disassemble) and polymerize (assembly) quickly, thereby allowing the cell to change its shape. During the polymerization process, the ATP that is bound to G-actin is hydrolyzed to ADP, which is bound to F-actin. ATP-actin subunits are present at the barbed ends of the filaments, and cleavage of the ATP molecules produces highly stable filaments bound to ADP. In consequence, it is expected that cofilin binds preferentially to highly stable (older) filaments ADP-actin filaments instead of ATP-actin filaments.