Configuration of clathrin trimers: evidence from electron microscopy.

We used a combination of electron microscopic techniques--negative staining, glycerol spraying with rotary shadowing, and quick-freezing followed by deep-etching--to study the configuration of clathrin trimers. All three approaches provide images indicating that the molecule is nonplanar and rather puckered at its center. Viewed from the convex (cytoplasmic) side, its arms display a consistent clockwise slew at their proximal/distal hinge. The most flexible part of the heavy chain may be the links between the distal portion of the leg and the terminal domain.