Figure 1.

GGA-deficient yeast have a defect in α-factor processing. (a) Colonies of wild-type (wt) cells, single-deletion mutants (gga1Δ and gga2Δ), or double-deletion mutants (gga1Δ/gga2Δ) were spotted onto a lawn of mating type a cells to test for the secretion of active α-factor. The reduced halo size surrounding the gga1Δ/gga2Δ colony when compared with the other three colonies indicates that less active α-factor is secreted in the double-deletion mutant. (b) Secreted α-factor was immunoprecipitated from the medium of metabolically labeled cells using an antibody that preferentially recognizes the precursor form. The gga1Δ/gga2Δ cells secrete mainly α-factor precursor.