Lecture 4: Nuclear Pore Complex Protein Transport

GTP & GDP and it’s importance

the hydrolization of GTP to GDP is where the energy for nuclear pore protein transport comes from.

GTP-ases

• proteins that can bind and hydrolyze GTP, making it GDP.

• The hydrolysis is energetically favorable and coupled with protein transport through nuclear pores 

GTP-ases shape and function is determined by

whether or not they are attached to GTP or GDP

How GTP-ases are regulated

through GAPs and GEFs, proteins that assist in the GTPases ability to work

GAPs

a GTP=ase activator protein that stimulates GTPases’s ability to HYDROLIZE GTP and create GDP

GEFs

a guanine exchange factor, promoting the GTPase to exchange GDP for GTP

Ran (itself) 

• type of GTPase that supplies energy for nuclear pore complex transport 

• can be bound to GDP or GTP, affecting its form and function 

• Has its own GAPS & GEFs that help Ran switch between RanGDP& RanGTP

What provides directionality to transport (explain the process and why this happens in particular )

cellular localization of the RanGAP & RANGEF

Cellular Localization of RanGAP & what it means

located inside the cytosol, meaning that RanGDP & GDP is highly abundant in the cytosol

Cellular Localization of RanGEF & what it means

located inside the nucleus, ensign that RanGTP & GTP is highly abundant in the nucleus 

Stepwise of protein transport in through nuclear pores 

1. Signal sequence is recognized by receptor (importins) & attaches to the protein [foldedl]

2. The importin carries the protein to the pore and goes through

3. The importin runs into RanGTP and drops the protein (cargo)

4. The importin leaves the nucleus and the RanGTP becomes RanGDP due to the high abundance of RanGAP in the nucleus

5. The importin drops the RanGDP, due to the change in shape (EW!)

Stepwise of protein transport out of  nuclear pores 

1. Exportins bind to RanGTP in order to be able to grab on to the cargo (proteins) 

2. They leave the nucleus 

3. RanGAP is in high affinity, so the RanGTP becomes RanGDP and the exporting let’s go, letting go of the cargo. 

Signal Sequences 

sequences of amino acids that tell signal receptors where the protein is meant otherwise be localized 

T or F: Proteins are fully folded during transport through ocular pores

True

Nuclear Pore complex

hole of tangled, unstructured proteins that act as a mesh to allow things less than 60k daltons in freely without energy

Improtins

Proteins that recognize signal sequences and bring proteins in