Sandbox 154: Difference between revisions

Line 10:

== Assembly ==

'''G-actin''' is the free monomeric form of actin which ~~transitions~~ to F-actin. The structures of globular and filamentous actin are distinct from one another in numerous ways, despite the fact that G-actin comprises F-actin. When the monomeric actin becomes polymerized into F-actin, the unit becomes flattened. G-actin appears to have more <scene name='Sandbox_154/1j6z_calcium/1'>~~Ca2+~~</scene> ~~ion~~ ligands in its structure, and also has the ligand RHO as opposed to 4-methyl histidine as found in the F-actin structure.

'''G-actin''' is the free monomeric form of actin which polymerizes to F-actin. The structures of globular and filamentous actin are distinct from one another in numerous ways, despite the fact that G-actin comprises F-actin. When the monomeric actin becomes polymerized into F-actin, the unit becomes flattened. G-actin appears to have more <scene name='Sandbox_154/1j6z_calcium/1'>calcium ion</scene> ligands in its structure, and also has the ligand RHO as opposed to 4-methyl histidine as found in the F-actin structure.

Formation of F-actin is a dynamic process of assembly and disassembly which has been termed “treadmilling”.

The transition between G- and F-actin begins with a stabilized oligomer of ATP-actin units formed through a nucleation-condensation type fold pattern<ref>pfaendtner</ref>. Addition of ATP-monomeric units to either end subsequently occurs, however, because of a difference in charge polarity in the two ends, there is preferential addition to what is termed the "plus (+) end" or the "barbed-end". On the opposite end, the "minus (-) end" or the "pointed end", there is preferential dissociation of actin units<ref>mitchinson</ref>. After attachment of the ATP-bound actin, hydrolysis of the ATP occurs yielding the ADP+Pi bound state. Subsequent loss of a Pi leaves the ADP-actin state<ref>chen</ref>. Because of the potential for addition or removal of monomeric units to occur at both ends, the assembly of F-actin may be described in terms of equilibrium. However, because the rate of ATP-actin association is ten-fold that of ADP-actin dissociation, the f-actin has the appearance of moving forward, or "treadmilling"<ref>clasier</ref>. ADP-actin monomers dissociate at the minus end and become recycled to ATP-actin so polymerization at the plus end may occur once again.

The transition between G and F-actin begins with a stabilized oligomer of ATP-actin units formed through a nucleation-condensation type fold pattern<ref>pfaendtner</ref>. Addition of ATP-monomeric units to either end subsequently occurs, however, because of a difference in charge polarity in the two ends, there is preferential addition to what is termed the "plus (+) end" or the "barbed-end". On the opposite end, the "minus (-) end" or the "pointed end", there is preferential dissociation of actin units<ref>mitchinson</ref>. After attachment of the ATP-bound actin, hydrolysis of the ATP occurs yielding the ADP and Pi bound state. Subsequent loss of a Pi leaves the ADP-actin state<ref>chen</ref>. Because of the potential for addition or removal of monomeric units to occur at both ends, the assembly of F-actin may be described in terms of equilibrium. However, because the rate of ATP-actin association is ten-fold that of ADP-actin dissociation, the f-actin has the appearance of moving forward, or "treadmilling"<ref>clasier</ref>. ADP-actin monomers dissociate at the minus end and become recycled to ATP-actin so polymerization at the plus end may occur once again.

== Structure ==

Sandbox 154: Difference between revisions

Navigation menu

Page actions

Page actions

Personal tools

Navigation

Search

Tools

@@ Line 10: / Line 10: @@
 == Assembly ==
 <applet load='1j6z' size='200' color='black' frame='true' align='left' caption='Globular Actin (G-actin): PDB identifier [http://www.rcsb.org/pdb/explore/explore.do?structureId=1J6Z/ 1J6Z].' scene='Sandbox_154/1j6z_black/2'/>
-'''G-actin''' is the free monomeric form of actin which transitions to F-actin. The structures of globular and filamentous actin are distinct from one another in numerous ways, despite the fact that G-actin comprises F-actin. When the monomeric actin becomes polymerized into F-actin, the unit becomes flattened. G-actin appears to have more <scene name='Sandbox_154/1j6z_calcium/1'>Ca2+</scene> ion ligands in its structure, and also has the ligand RHO as opposed to 4-methyl histidine as found in the F-actin structure.
+'''G-actin''' is the free monomeric form of actin which polymerizes to F-actin. The structures of globular and filamentous actin are distinct from one another in numerous ways, despite the fact that G-actin comprises F-actin. When the monomeric actin becomes polymerized into F-actin, the unit becomes flattened. G-actin appears to have more <scene name='Sandbox_154/1j6z_calcium/1'>calcium ion</scene> ligands in its structure, and also has the ligand RHO as opposed to 4-methyl histidine as found in the F-actin structure.
 Formation of F-actin is a dynamic process of assembly and disassembly which has been termed “treadmilling”.
-The transition between G- and F-actin begins with a stabilized oligomer of ATP-actin units formed through a nucleation-condensation type fold pattern<ref>pfaendtner</ref>. Addition of ATP-monomeric units to either end subsequently occurs, however, because of a difference in charge polarity in the two ends, there is preferential addition to what is termed the "plus (+) end" or the "barbed-end". On the opposite end, the "minus (-) end" or the "pointed end", there is preferential dissociation of actin units<ref>mitchinson</ref>. After attachment of the ATP-bound actin, hydrolysis of the ATP occurs yielding the ADP+Pi bound state. Subsequent loss of a Pi leaves the ADP-actin state<ref>chen</ref>. Because of the potential for addition or removal of monomeric units to occur at both ends, the assembly of F-actin may be described in terms of equilibrium. However, because the rate of ATP-actin association is ten-fold that of ADP-actin dissociation, the f-actin has the appearance of moving forward, or "treadmilling"<ref>clasier</ref>. ADP-actin monomers dissociate at the minus end and become recycled to ATP-actin so polymerization at the plus end may occur once again.
+The transition between G and F-actin begins with a stabilized oligomer of ATP-actin units formed through a nucleation-condensation type fold pattern<ref>pfaendtner</ref>. Addition of ATP-monomeric units to either end subsequently occurs, however, because of a difference in charge polarity in the two ends, there is preferential addition to what is termed the "plus (+) end" or the "barbed-end". On the opposite end, the "minus (-) end" or the "pointed end", there is preferential dissociation of actin units<ref>mitchinson</ref>. After attachment of the ATP-bound actin, hydrolysis of the ATP occurs yielding the ADP and Pi bound state. Subsequent loss of a Pi leaves the ADP-actin state<ref>chen</ref>. Because of the potential for addition or removal of monomeric units to occur at both ends, the assembly of F-actin may be described in terms of equilibrium. However, because the rate of ATP-actin association is ten-fold that of ADP-actin dissociation, the f-actin has the appearance of moving forward, or "treadmilling"<ref>clasier</ref>. ADP-actin monomers dissociate at the minus end and become recycled to ATP-actin so polymerization at the plus end may occur once again.
 == Structure ==