Return to Sender
Studying the structures of proteins involved in membrane fission and fusion, while removed from the health implications of membrane dynamics, can also reveal how membranes are sculpted. HHMI investigator Jonathan Goldberg studies the proteins involved in returning misdirected proteins from the Golgi back to the ER. Proteins that take this path when they shouldn't are marked with a “return to sender” chemical signal.
“If the forward transport step and the reverse transport step weren't properly controlled, from one to the other, the ER membrane and proteins would all end up in the Golgi or vice versa,” says Goldberg.
Goldberg, a structural biologist at Memorial Sloan Kettering Cancer Center, has snapped atomic-level images of COPII vesicle coats, revealing which parts of the coat molecules play each role in vesicle formation.
Now he's studying the vesicles that travel the reverse route, from the Golgi to the ER. Each structure helps paint a picture of what the vesicles look like and how they form. Membranes are not likely to change shape unless proteins coax them to move. Goldberg's structures show how vesicle coat proteins can pull a membrane segment into a bubble.
These proteins are self-assembling, ready to form a sphere. Because they have some points of attachment to the membrane, as they form a sphere they sculpt the membrane into a bud, Goldberg explains. “It's a really beautiful mechanism.”
- Sarah Williams
HHMI Bulletin, February 2010