So I work in a lab that studies actin so why not print out the actin structure so I can learn more about it?
Here is a nice overview of actin and what it does. Briefly, actin is polymerized into filaments for lots of different purposes inside the cell.
Here are two structures that show actin bound to Dnase I (ATN1 on pdb; left) and actin bound in a filament (2Y83 on pdb; right). Notice how the pointed-end (that's the bottom in the picture) is more compressed in the one on the right, that is supposed to fit in a filament. Whereas the one on the left has the pointed end sort of splayed out, because there's supposed to be a DNase I bound to the DNase I loop (biologists are creative aren't they). Haven't had a chance to print out more of the right structure so I can make a filament, but I will do that as soon as possible.
Also I need to work out a concrete set of scale. I sort of eyeballed these and it shows, the one on the right is noticeably larger.
Woo! First protein structure print. You can see I was messing with options so the rightmost one came out stringy and hole-y.