FIGURE 4-38 Coated vesicles can be purified by binding to an antibody specific for a vesicle surface protein and linkage to bacterial cells. In this example, a suspension of membranes from rat liver is incubated with an antibody specific for clathrin, a protein that coats the outer surface of certain cytosolic vesicles. To this mixture is added a suspension of killed Staphylococcus aureus bacteria, whose surface membrane contains protein A, which binds to the constant (Fc) region of antibodies. (a) Interaction of protein A with antibodies bound to clathrin-coated vesicles links the vesicles to the bacterial cells. The vesicle-bacteria complexes can then be recovered by low-speed centrifugation. (b) A thin-section electron micrograph reveals clathrin-coated vesicles bound to an S. aureus cell. See E. Merisko et al., 1982, J. Cell Biol. 93:846.

[Micrograph courtesy of George Palade.]