Intracellular membrane trafficking Flashcards
What is gated /protein translocation /vesicular transport ?
each transfer is mediated by sorting signals .
What does Vesicle budding and fusion maintain ?
Maintain compartmental , topology and integrity
What occurs during Exocytosis ?
A transport vesicle fuses with the plasma membrane , its content is released into extracellular space, vesicle membrane becomes continuous with plasma membrane
What occurs during endocytosis ?
A plasma membrane patch internalised forming a transport vesicle , its content desires from extracellular space .
What is Cargo?
Transport vesicles continually bud off from the membrane and fuse with another carrying membrane components and soluble lumen molecules known as cargo
What do vesicles do ?
They carry materials as cargo from lumen and the membrane of donor compartment to membrane and lumen of target compartment.
What does Vesicle transport do ?
Perform it functions each transport vesicle buds from compartments must be selective .It makes take up appropriate molecules an fuse with target membrane.
Such as a vesicle carrying cargo to Golgi apparatus example must exclude proteins and only fuse with Golgi apparatus and not others .
What are the various types of Coated vesicles ? 3
Clarin Coates
COPI coated
COP11 coated
What do vesicles bud from specialised coated regions ?
Have distinctive cage of proteins covering cystolic surface .
What are the two main functions of the coat ?
Outer coats layer assembles into a curve . basketball .lattice and deforms the membrane pat cnad thereby shapes vesicles
What is the Function of Clarthrin coated vesicles ?
Vesicles transport material from the plasma membrane to the Golgi apparatus
What is COPI AND COPII coated vesicles ? Function
Transport materials from ER- Golgi
Clarthrin coated vesicles ( the first coasted vesicles to be identified )
Transport material from plasma membrane between endosomal and Golgi compartments
What is the major components of clathrin coated vesicles ?
Clathrin itself ,forms outer layer of the coat
Each Clarathin subunits consists of three large three small polypeptide chain that together form a three legged structure called triskelion
Clathrin triskelion dissemble into a basketlike framework of hexagon and pentagons to form buds on cystolic surface of membranes
What about under appropriate conditions ,isolated triskelions>?
Spontaneoulsy self assemble into typical polyhedral cages in a test tube ,even in absence of the membrane vesicles that these baskets enclose
What is Adaptor proteins function ?
Select cargo into clathrin coated vesicles
Another major coat component in clathrin coated vesicles from discrete inner layer of the coat , positioned between clathrin cage and membrane .
Bind the clathrin coat to membrane /trap variations transmembrane proteins including transmembrane receptor inside vesicles known as cargo receptors
Adaptor proteins select a specific set of transmembrane proteins , together with soluble proteins interact with them , package them into newly formed clathrin coated transport vesicle
Dynamin is one of the examples of adaptor proteins
There are several types of adaptor proteins , each specific for cargo receptors ?
Found in other coats , they bind to phosphoinsited which not only have a major role in directing when where coats assemble in the cell , used much widely as molecular makers of compartments help to control ventricular traffic .
What is the role of adaptor proteins AP2 ?
AP2 serves as well understood example , when it binds to specific phosphorylated , phosphatidylinositol lipid it alters the conformation , exposing binding sites for cargo receptors /Lipid head group enhancing binding of AP2 to membrane
Acts as a coincidence detector
Upon binding , the induce membrane curvature , makes binding of additional AP2 proteins in proximity
Specificity of targeting is mediated through RAB proteins
- Rab proteins are GTPases , each Rab proteins associated with one or more membrane enclosed organelles
Interact with Rab effector on target membrane
Snare proteins dock residues to the target and catalyse the fusion of the two bilayer
Once a V-snare and t -snare have mediated the fusion of a transport residue they dissemble
The dissociations of SNARE complex .
Once a V -SNARE and T-SNARE have mediated the fusion of transport vesicles they disassemble
Crucial to ensure that only appropriate membrane fuse .
What are the proteins and their organelle ?
RAB 1 - ER and Golgi complex
RAB 2 - Cis Golgi network
RAB 3A - Synaptic vesicles , secretory residues
RAB 4 - Recyling endosomes
RAB 5 - Early endosomes ,plasma membrane .clarathin coates vesciles
RAB 6 - Medial and trans GOLGI
RAB 7 - Late endosomes
RAB 8 - Cilia
RAB 9 - Late Endosomes trans Golgi
