<P> At the cytokinesis furrow , it is the actin - myosin contractile ring that drives the cleavage process , during which cell membrane and wall grow inward , which eventually pinches the mother cell in two . The key components of this ring are the filamentous protein actin and the motor protein myosin II . The contractile ring assembles equatorially ( in the middle of the cell ) at the cell cortex ( adjacent to the cell membrane ) . Rho protein family ( RhoA protein in mammalian cells ) is a key regulator of contractile ring formation and contraction in animal cells . The RhoA pathway promotes assembly of the actin - myosin ring by two main effectors . First , RhoA stimulates nucleation of unbranched actin filaments by activation of Diaphanous - related formins . This local generation of new actin filaments is important for the contractile ring formation . This actin filament formation process also requires a protein called profilin , which binds to actin monomers and helps load them onto the filament end . Second , RhoA promotes myosin II activation by the kinase ROCK , which activates myosin II directly by phosphorylation of the myosin light chain and also inhibits myosin phosphatase by phosphorylation of the phosphatase - targeting subunit MYPT . Besides actin and myosin II , the contractile ring contains the scaffolding protein anillin . Anillin binds to actin , myosin , RhoA and CYK - 4 , and thereby links the equatorial cortex with the signals from the central spindle . It also contributes to the linkage of the actin - myosin ring to the plasma membrane . Another protein , septin , has also been speculated to serve as a structural scaffold on which the cytokinesis apparatus is organized . Following its assembly , contraction of the actin - myosin ring leads to ingression of the attached plasma membrane , which partitions the cytoplasm into two domains of emerging sister cells . The force for the contractile processes is generated by movements along actin by the motor protein myosin II . Myosin II uses the free energy released when ATP is hydrolysed to move along these actin filaments , constricting the cell membrane to form a cleavage furrow . Continued hydrolysis causes this cleavage furrow to ingress ( move inwards ) , a striking process that is clearly visible through a light microscope . </P>
<P> At the cytokinesis furrow , it is the actin - myosin contractile ring that drives the cleavage process , during which cell membrane and wall grow inward , which eventually pinches the mother cell in two . The key components of this ring are the filamentous protein actin and the motor protein myosin II . The contractile ring assembles equatorially ( in the middle of the cell ) at the cell cortex ( adjacent to the cell membrane ) . Rho protein family ( RhoA protein in mammalian cells ) is a key regulator of contractile ring formation and contraction in animal cells . The RhoA pathway promotes assembly of the actin - myosin ring by two main effectors . First , RhoA stimulates nucleation of unbranched actin filaments by activation of Diaphanous - related formins . This local generation of new actin filaments is important for the contractile ring formation . This actin filament formation process also requires a protein called profilin , which binds to actin monomers and helps load them onto the filament end . Second , RhoA promotes myosin II activation by the kinase ROCK , which activates myosin II directly by phosphorylation of the myosin light chain and also inhibits myosin phosphatase by phosphorylation of the phosphatase - targeting subunit MYPT . Besides actin and myosin II , the contractile ring contains the scaffolding protein anillin . Anillin binds to actin , myosin , RhoA and CYK - 4 , and thereby links the equatorial cortex with the signals from the central spindle . It also contributes to the linkage of the actin - myosin ring to the plasma membrane . Another protein , septin , has also been speculated to serve as a structural scaffold on which the cytokinesis apparatus is organized . Following its assembly , contraction of the actin - myosin ring leads to ingression of the attached plasma membrane , which partitions the cytoplasm into two domains of emerging sister cells . The force for the contractile processes is generated by movements along actin by the motor protein myosin II . Myosin II uses the free energy released when ATP is hydrolysed to move along these actin filaments , constricting the cell membrane to form a cleavage furrow . Continued hydrolysis causes this cleavage furrow to ingress ( move inwards ) , a striking process that is clearly visible through a light microscope . </P>
when does a cell membrane pinch together to divide
when does a cell membrane pinch together to divide
the cleavage process
the cleavage process