Proteasomes are the cell’s garbage disposals, where excess or toxic proteins are "gobbled up" and recycled. They are made up of discrete units that comprise the “lid” (seen in color in the figure, at left), the “base” and the “core” (the last two in gray).
A team of Yale researchers is using advanced chemistry and imaging technology to describe how the lid forms and then joins to the base. Surprisingly, the crucial final step in assembly is triggered by the binding of a single helix, or spiral-shaped molecule, to the lid precursor, Mark Hochstrasser and team report in the Oct. 8 issue of the journal Cell.
“It is like when a thumb is lifted from a fist, the hand can open and go to work,” Hochstrasser said. The dramatic protein reconfiguration is similar to that seen in formation of viral particles and may be common to all forms of life.