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Where are Rab proteins found?

Rab proteins form the largest branch of the Ras superfamily of GTPases. They are localized to the cytoplasmic face of organelles and vesicles involved in the biosynthetic/secretory and endocytic pathways in eukaryotic cells.

What proteins are involved in vesicular transport?

The coats of clathrin-coated vesicles are composed of two types of protein complexes, clathrin and adaptor proteins, which assemble on the cytosolic side of membranes (Figure 9.31). Clathrin plays a structural role by assembling into a basketlike lattice structure that distorts the membrane and drives vesicle budding.

What does the Rab protein do?

Rab proteins are small guanosine triphosphatases which regulate protein transport along the endocytic and exocytic pathways in all cell types. Rabs participate in vesicle budding, membrane fusion, and interactions with the cytoskeleton.

How Rab proteins guide transport vesicles to their target membrane?

A family of Rab proteins functions as vesicle targeting GTPases. Being incorporated with v-SNAREs into budding transport vesicles, the Rab proteins help ensure that the vesicles deliver their contents only to the appropriate membrane-enclosed compartment: the one that displays complementary t-SNARE proteins.

What is a Rab effector?

Rab effectors, defined as proteins that interact specifically with the GTP-bound from of a Rab GTPase, come in many flavours and include molecular tethers, fusion regulators, motors, sorting adaptors, kinases, phosphatases, components of membrane contact sites and Rab regulators (Gillingham et al., 2014).

What are some examples of vesicular transport?

Any process in which a cell forms vesicles from its plasma membrane and takes in large particles, molecules, or droplets of extracellular fluid; for example, phagocytosis pinocytosis and receptor-mediated endocytosis.

How are proteins transported by vesicles?

Vesicular protein transport involves the selective recruitment of cargo into the vesicles, controlled formation of the vesicle, partial uncoating and transport to the target membrane/organelle, binding to and fusion with the target membrane, followed by the exchange of the cargo molecules from the limited vesicular …

How are Rab proteins activated and what is their function?

Rab proteins are peripheral membrane proteins, anchored to a membrane via a lipid group covalently linked to an amino acid. A guanine nucleotide exchange factor (GEF) catalyzes the conversion from GDP-bound to GTP-bound form, thereby activating the Rab.

What is the function of Rab in the targeting of proteins to their final destination?

Rabs use the guanine nucleotide-dependent switch mechanism common to the superfamily to regulate each of the four major steps in membrane traffic: vesicle budding, vesicle delivery, vesicle tethering, and fusion of the vesicle membrane with that of the target compartment.

Where are the Rab proteins located in the cell?

The Rab family of small GTPases, comprising approximately 70 members, is the master regulators of intracellular vesicle transport. Each Rab protein is localized to the cytoplasmic surface of a distinct membrane bound organelle [23], [24], [25] and appears to control a specific membrane transport pathway.

How are Rabs implicated in the formation of vesicle?

Most of the Rabs are ubiquitously expressed proteins and have been implicated in vesicle formation, vesicle motility/delivery along cytoskeleton elements and docking/fusion at target membranes through the recruitment of effectors. Functional impairments of Rabs affecting transport pathways manifest different diseases.

How are Rab proteins used in the transcytic pathway?

Rab proteins in the transcytic pathway Transcytosis is a process by which various macromolecular cargos are transported from one side of a cell to the other within a membrane bounded carrier (s). This strategy is used by multi-cellular organisms to selectively move materials between two different environments.

Which is Rab protein is required for vesicle trafficking?

The first Rab gene was identified in S. cerevisiae and named as Sec4 / Ypt (Yeast protein transcript) [15] which encodes a small G protein that is required for vesicle trafficking from the Golgi apparatus to plasma membrane [16]. Rab proteins are the mammalian homologs.