Question

5. Phosphoinositides are molecular identity markers on the surface of organelles. A family of G-proteins also serves as a membrane marker and plays a role in vesicle targeting. Name the family and describe its role in vesicle targeting.

Answer 1

some g-proteins have been found associated with the golgi,an intracellular network of membranes that receives proteins from the ER (endoplasmic reticulum) and ancts as a processing and sorting hub for these proteins before they are trafficked to their destination.

• proteins are transported to the golgi from ER in vesicles coated witH COPI,and fusion of thse vesicles with the golgi requires the small monomeric guanosine triphosphate(GTPase)Arf1 and its GEFs and GTPase-activating proteins(GAPs).
• central in ensuring that cargoes are delivered to their correct destinations are the Rab GTPases,a large family of small GTPases that control membrane identity and vesicle budding ,uncoating,motility,and fusion through the recruitment of effector proteins,such as sorting adapters,tethering factors,kinases,phosphates and motors.
• cross talk between multiple Rab activators,ensures the spatiotemporal regulation of vesicle traffic.functional impairments of Rab pathways are associated with diseases, such as immunodeficiencies,cancer and neurological disorderrs.
• there approximately 60 different rab GTPases in humans that are associated with distinct intracellular membranes