What was the name of that chaperone protein you were talking about?

Dr. Thompson has fully redeemed himself, in my opinion. Yes, organic chemistry is a hard class, but it has become a class that inspires in me all sorts of questions - questions that he is willing and capable of answering and then giving even more information. The closer we drift toward biochemistry, the more excited I get about the subject material. I can see more and more of it complementing what I know about cellular biology.

Today we started off slightly off-topic with a question about proteins from another girl. I don't remember what it was, but the important part is that somehow the topic of chaperone proteins (chaperonins) came up. Chaperonins are cell proteins that help fold other proteins into their proper tertiary and quaternary structures. There are many different chaperonins, but one of particular interest is the GroEL-GroES complex.

The GroEL-GroES complex is found inside E. coli. It has by far the broadest range of "clients," or proteins it assists in folding. The exact processes by which it transforms the peptide chains are unknown, but some of the basics are understood. GroEL is a barrel-shaped, 14-unit polypeptide (in the picture to the left, the blue unit + the green one) that does the actual folding of the protein. GroES is a 7-unit polypeptide that forms the lid of the barrel (the red parts of the picture). Unfolded peptide chains are attracted to the complex somehow. One end of the chain is bonded to a non-polar site on the inside of GroES. This bonding triggers the lid to close, guiding the peptide into the barrel. Once GroES had covered GroEL, GroEL rotates so as to remove the non-polar site the peptide was bonded to thereby leaving the chain sitting unattached inside the barrel. Through the rotating of the barrel pieces and other unknown kinds of craziness, the complex is able to fold the new protein into its proper shape. Once folding is complete, the barrel-closing procedure is reversed and the fully functional new protein is released into the cytosol.

The most stunning thing is GroES-GroEL's ability to fold hundreds of different kinds of proteins. It's not like the chemical characteristics of the primary and secondary structures of some specific protein interact with the barrel in a highly specified way. No, this cell machine can fold hundreds of dramatically different peptide chains into dramatically different proteins. And, as is the case with most cell machines, it does its job with a great deal of accuracy. Whenever I learn about structures like these, I can't help but think, "Whoa. God is really cool and smart."

This information about GroEL-GroES only raises more questions for me (no surprise there). The biggest on my mind at the moment is whether or not there are chaperonins that fold molecules so that the hydrophobic regions are on the outside. Then they could act within the plasma membrane. Or maybe they have a hydrophilic region and a hydrophobic region, the former being anchored in the phosphate heads of the phospholipid bilayer and the latter chilling in the non-polar inner zone of the bilayer.