GYP1

Gyp1, short for GTPase-activating protein 1, is a name used for a family of enzymes that regulate small GTPases by accelerating their intrinsic GTP hydrolysis. The most studied instance is in the budding yeast Saccharomyces cerevisiae, where Gyp1p is a Rab family GTPase-activating protein. Rab GTPases act as molecular switches that control vesicular trafficking steps between organelles; Gyp1p inactivates these switches, contributing to the proper timing and directionality of transport along the secretory and endocytic pathways. Gyp1p belongs to a larger family of RabGAP proteins characterized by a catalytic GAP domain and, in many cases, localization signals that target membranes such as the Golgi apparatus and endosomal compartments.

Through genetic and biochemical studies, Gyp1p has been implicated in regulating traffic from the Golgi to endosomes and to the vacuole, and it interacts genetically with other components of the vesicular trafficking machinery. Deletion or loss of GYP1 function can lead to accumulation of transport intermediates and partially defective cargo sorting, especially under stress conditions.

Beyond yeast, GYP1-family proteins have been identified in other fungi and in higher eukaryotes, where they are expected to regulate Rab GTPases similarly, although substrate specificities and cellular roles can vary substantially by organism. In summary, Gyp1 denotes a RabGAP that contributes to the control of vesicle trafficking by switching off Rab GTPases, thereby shaping the flow of cargo through the cell.