we're continuing our studies in chapter 22 on protein synthesis and in this lesson we'll be looking at protein folding in particular we want to look at protein folding as it relates to the activity of molecular chapon they use the energy of ATP hydrolysis to help proteins refold they can do this in a number of different ways we're going to look at three molecular chapon first we'll look at trigger Factor this is the first first molecular chapon that most proteins encounter because it positions itself just outside the exit tunnel of the ribosome as you can see by examining the figure on the right trigger factor is highlighted in red green blue and yellow and it is bound to certain regions of the ribosome perfectly positioned to bind to the nent polypeptide highlighted in magenta as it comes through the exit channel of the ribosome as the nent polypeptide exits the ribosome the trigger Factor will bind a hydrophobic patches of the protein these would normally be folded up within the protein trigger Factor then may release the polypeptide so that it can fold up on its own or it may hand off the protein to another chaperon for further assistance in folding another type of molecular chaperon is DNA K it is not associated with the ribosome this molecular chaperon clamps down on the protein and then releases it thereby allowing it to refold itself again it binds to hydrophobic patches of the protein that would normally be folded within the internal regions so the fact that these patches are exposed means that the protein is misfolded in our surface model here DNA is highlighted in green and the target protein in yellow as you can see it clamps down and surrounds the target protein lastly we have the complex grow L grow s we have considered this in an earlier chapter growel is a complex of two heptameric rings seven membered rings and protein folding occurs inside each of these two rings each of the seven subunits in each of the Rings binds and hydes one ATP so seven ATP molecules per ring in the illustration at the top of the slide you can see that the two rings are centrally positioned back to back within the complex a misfolded protein is bound by growel No Doubt recognizing those exposed hydrophobic patches and at the same time the grow L ring also binds 7 m molecules of ATP it is The Binding of the growes cap that triggers the release of the peptide inside the barrel of growel subsequent hydris of ATP releases the peptide from growel still within that growel chamber thereby giving it an opportunity to refold itself as in the case of every molecular chaperon it doesn't actually fold the protein it just gives it a protected environment so that it can refold itself in our next video Lesson we want to look at some of the possible post transational modifications to protein