Compartments & Protein Transport (Nucleus & Cytosol)

The Autogenous Model

In this theory, you start with a single cell, & it is specialized.

“Inside Out” Theory (Endosymbiosis)

In this theory, you start with a cell & it sends projections from membrane; projections grow around other cells.

Topographically Similar

This is when two compartments share with each other; they have access to each other.

Topographically Different

This is when two compartments are completely separate by a membrane.

Signal Sequences and Signal Patches

These show proteins where they need to go.

Gated Transport

This is when selective “gates” between compartments transport specific macromolecules into topographically similar spaces.

Transmembrane Transport

This makes use of membrane-bound protein complexes to directly move specific proteins from one compartment to a topographically different compartment.

Vesicular Transport

This is when membrane-enclosed transport intermediates from one compartment to another topographically different compartment (put it in a box & ship it).

nucleus; cytoplasm

Gated transport occurs between the ______________ and the _________________.

Nucleoporins

This is a family of proteins that are the building blocks of the nuclear pore complex (make up the nuclear pore).

Virtual Gate Model

This is the thermodynamic exclusion of cargo in the pore; as something comes, it repels.

Selective Phase Model (unsaturated)

This is when FG filaments interact & form a selective 3D sieve to exclude cargo by a 3D sieve; less structure.

Selective Phase Model (saturated)

This is when FG filaments form the maximum number of filaments resulting in a highly ordered mesh w/ even pore size.

Importin-a

This recognizes & binds to cargo with the nuclear localization signal (step 1).

Importin-B

This binds to Importin-a (step 2).

________________ is the actual transport factor through the nuclear pore complex.

Ran-GAP

This is the GTPase-activating protein; causes GTP to hydrolyze (GTP to GDP).

Ran-GEF

This is the Guanine Exchange Factor: removes GDP & replaces it with GTP.

….

Explain the process of Nuclear Import:

Nuclear Localization Signal

This is the amino acid sequence of the cargo protein (can be linear or as a patch anywhere in the protein).

Nuclear Import Receptors (a and B)

These bind to the nuclear localization signal of cargo proteins.

Ran-GDP and Ran-GTP

These are different forms of the Ran molecular switch protein bound to either GDP or GTP; Ran-GTP causes the dissociation of cargo from importins.

….

Explain the process of Nuclear Export:

TREX Proteins

This is an adaptor for the nuclear export of mRNA.

SR Proteins

This is an adaptor for nuclear export of mRNA.

Tap p15

This is the nuclear export receptor protein (doesn’t bind to RNA, it binds to TREX & SR to move RNA).

….

Explain the process of the Nuclear Export of hnRNA: