The identification of 23 complementation groups required for post-translational events in the yeast secretory pathway.

See also: Novick, P., Ferro, S. and Schekman, R. "Order of events in the yeast secretory pathway," Cell, 25, 1981, 461-469.

In 1979 Schekman devised a genetic selection for temperature-conditional secretion-defective yeast mutants (sec mutants) based on an increase in cell density associated with accumulation of secretory proteins inside the mutant cells. This approach resulted in the discovery of some 23 SEC genes that encode components of the basic molecular machinery essential for vesicle-mediated protein transport along the secretory pathway.

In 2013 Scheckman shared the Nobel Prize in Physiology or Medicine with James E. Rothman and Thomas C. Südhof "for their discoveries of machinery regulating vesicle traffic, a major transport system in our cells."