Credit: Yanyan Zhao/Stanford University
A SLAC-Stanford study revealed four intermediate steps in folding a human protein called tubulin, all directed by the inner walls of a cellular machine called TRiC (yellow). The process starts when a strand of tubulin enters the TRiC chamber. One end (green) hooks into the inner chamber wall; then the other end (light blue) attaches in another spot and folds, followed by the green end and two more folds of the middle sections (dark blue and red). The folding is directed by areas of electrostatic charge on the inner wall and by “tails” of protein dangling from the inner wall, which hold and stabilize the protein in the right configuration for the next step in folding. The protein core (dark blue) contains pockets (orange) where GTP, a molecule that stores and releases energy to power the cell’s work, plugs in.