Actin

[zmike]

My textbook says that actin grows from the + end ONLY BUT
shows a diagram where it's associating and dissocating AT BOTH ends and says that how treadmilling works. help?

thanks

[bobo]

mmmm !

I can ensure you that the actin grow only from the + ends just like microtubule
but i really dont have any idea about that diagram!!

hope someone could explane

[MrMistery]

both actin and microtubules can grow both at the (+) and (-) ends.
with actin, the reason actin in fact only grows at the plus end is that the concentration of monomers inside the cell is not high enough for the actin to grow at the (-) end also. If the concentration would be higher, actin would grow from both ends.

With MTs, the reason they only grow on the (+) end is that the (-) end is capped (bound by proteins such as gamma-tubulin). So nothing interesting happens at the (-) end with MTs, all the action is at the (+) end