Heat shock protein 90 (HSP90) has a greater impact on the appearance of new traits than previously expected, according to two new articles. HSP90 belongs to a class of proteins called chaperones, which help other proteins in the cell fold properly, prevent protein clumping, and escort improperly made proteins to be recycled. These vital functions become even more important when a cell is stressed by heat, cold, toxins or other hardships that affect protein folding.