Lecture 14 - Vesicular trafficking Flashcards
What is the role of GTPases in transport vesicle formation?
What is the role of GTPases in transport vesicle formation?
Answer: GTPases play a crucial role in regulating various steps of transport vesicle formation. They act as molecular switches, cycling between active (GTP-bound) and inactive (GDP-bound) states, and their activation triggers specific events during vesicle formation, such as coat assembly, membrane budding, and vesicle scission.
Which GTPase is involved in COPII vesicle formation?
The GTPase involved in COPII vesicle formation is called Sar1. When activated by GTP binding, Sar1 recruits COPII coat proteins to the ER membrane, initiating the assembly of COPII-coated vesicles.
What are adaptors in transport vesicle formation?
Adaptors are proteins that link cargo molecules to coat proteins during vesicle formation. They recognize specific sorting signals on cargo molecules and interact with both the cargo and the coat proteins, facilitating cargo concentration and incorporation into transport vesicles.
What is the role of adaptors in clathrin-coated vesicle formation?
In clathrin-coated vesicle formation, adaptors, such as AP (adaptor protein) complexes, connect cargo molecules to clathrin triskelia, facilitating cargo selection and clustering. They also help in the deformation of the membrane and the budding of clathrin-coated vesicles.
What are coat proteins in transport vesicle formation?
Coat proteins are multimeric protein complexes that assemble on the cytoplasmic surface of cellular membranes to drive vesicle formation. They form a scaffold that deforms the membrane and helps in cargo concentration, as well as recruit other factors involved in vesicle formation and fission.
What is the role of clathrin in vesicle formation?
Clathrin is a major coat protein involved in the formation of clathrin-coated vesicles. It assembles into a lattice structure on the cytoplasmic side of the membrane, providing structural support for vesicle formation and aiding in cargo selection and budding.
How do coat proteins contribute to vesicle scission?
Coat proteins, such as clathrin or COPII, recruit accessory factors that promote membrane curvature and bud formation. These factors, along with the GTPase activity of the associated GTPases, create mechanical forces that drive the final scission of the vesicle from the donor membrane.
What happens to coat proteins after vesicle formation?
After vesicle formation, coat proteins are typically shed from the vesicles. The disassembly of coat proteins can be facilitated by factors such as ATPases, which promote the release of the coat from the vesicle and its recycling for subsequent rounds of vesicle formation.
What is cargo selection in vesicle transport?
Cargo selection is the process by which specific molecules or proteins are recognized and sorted for transport into vesicles, ensuring their delivery to the appropriate cellular compartments.
How are cargo molecules recognized during cargo selection?
Cargo molecules are recognized during cargo selection through specific sorting signals or motifs present on their molecular structure. These signals act as tags that allow them to interact with receptors or adaptors involved in vesicle formation.
What are sorting signals?
Sorting signals are short amino acid sequences or structural motifs present on cargo molecules that direct their specific recognition and incorporation into transport vesicles during cargo selection.
What are the different types of sorting signals?
The different types of sorting signals include signal peptides, transmembrane domains, cytoplasmic tails, lipid modifications, or protein-protein interaction motifs. These signals help determine the destination and mode of transport for cargo molecules.
What are adaptors in cargo selection?
Adaptors are proteins that bridge the interaction between cargo molecules and coat proteins during vesicle formation. They bind to both cargo molecules and coat proteins, facilitating cargo concentration and incorporation into transport vesicles.
How do adaptors contribute to cargo selection?
Adaptors play a critical role in cargo selection by recognizing and binding to cargo molecules via their sorting signals. They also interact with coat proteins, linking the cargo to the coat and facilitating its incorporation into the forming transport vesicles.
