Chaperones' Influence On Protein Folding

Most protein-folding studies have focused on the folding of isolated proteins, so the often profound influence of chaperone proteins on the folding of other proteins remains poorly understood. Sander J. Tans of the FOM Institute for Atomic & Molecular Physics, in Amsterdam, and coworkers have now tried to address this problem by using optical tweezers and molecular dynamics to study the role of the chaperone SecB on the folding of maltose binding protein (MBP) (Science 2007, 318, 1458). They find that extended (unfolded) MBP folds to an intermediate state called a "molten globule," either in the presence or absence of SecB. And they show that SecB binds to extended MBP or its molten globule and prevents the protein from fully folding to its native state. MBP must be extended to be transportable through cell membranes, and the researchers speculate that SecB's hindrance of folding means that less energy is required for transmembrane transport of MBP.