The C-terminal tetrapeptide of phaseolin is sufficient to target green fluorescent protein to the vacuole

Phaseolin is a vacuolar storage glycoprotein synthesized as a precursor with a short C-terminal propeptide. We have recently shown that deletion of the last four C-terminal amino acids (AFVY, which are part of, or constitute the propeptide) abolishes vacuolar targeting, causing phaseolin to be secreted. Here we provide biochemical and microscopical evidence that the AFVY tetrapeptide, when fused to a secreted version of green fluorescent protein (GFP), inhibits GFP secretion and leads to its accumulation in vacuoles, where it is processed. This demonstrates that the tetrapeptide contains sufficient information for vacuolar sorting.