Protein Trafficking

Question 1

Three different mechanisms of protein trafficking

Answer 1

1. Gated transport: move between topologically equivalent compartments through gates
2. transmembrane transport: move between topologically distinct compartments through channels
3. vesicular transport: soluble cargo molecules and bilayer move between topologically equivalent compartments carried within vesicles

Question 2

examples of transmembrane transport

Answer 2

1. import of proteins from the cytosol into the mitochondria or chloroplasts
2. co-translational translocation between the cytosol and the ER

Question 3

signal sequences

Answer 3

proteins contain built in signals that target them to specific compartments. signals are built into the primary, secondary, or tertiary protein structure. signals are recognized by specific receptor proteins

Question 4

receptors recognized two types of signals:

Answer 4

1. signal sequences: linear amino acid motifs within the primary structure located at the N or C terminus or within the middle of a protein
2. signal patches: formed by two or more regions of a protein that come together when the protein assumes secondary or tertiary structure.

Question 5

examples of gated transport

Answer 5

nuclear import/export

Question 6

examples of vesicular transport (not really a specific example given)

Answer 6

a vesicle buds from the ER containing cargo and is fused to another topologically equivalent compartment. membrane topology is preserved as well as orientation.