Cell Biology Unit 2

Euk. mRNAs are translated on ----- ER or in the cytosol.

------- is the default location for proteins w/o signal sequences.

Short but specific protein tags termed ------ sequences within protein direct protein to specific organelles (ER, nucleus, peroxisome, mitochondria, chloroplast)

True or False?

3°/4° structure of the protein is disrupted during nuclear import (or export). Even ribosomal subunits, which are huge can not be exported!

• True

• False (it's not)

For import, nuclear localization sequences (NLS) in "cargo proteins" (Lysine/Arginine rich, usually at N-terminus) bind to -------, which direct them through the ------- ----.

Dissociation of importin from cargo proteins requires binding of ------- protein (GTP-binding protein), export of importins back to the cytoplasm (and release from Ran) requires --- ----------

The nuclear pore is made of a large complex of ----------- proteins.

True or False?

Large and small molecules diffuse or are transported in either direction through the pore.

• True

• False (one direction)

True or False?

The nuclear pore channel is very large, so 3°/4°structure of protein complexes is not disrupted during nuclear import (or export). Even ribosomal subunits, which are huge, can be exported.

• True

• False (it is disrupted)

Functions in metabolism, especially oxidation (break down) of long-chain fatty acids and removal of toxic molecules. Present in most cell types in all eukaryotes. Very high internal enzyme concentration sometimes crystallizes

• Lysosome

• Peroxisome

Peroxisome: Functions in metabolism, especially --------- (break down) of long-chain fatty acids and removal of toxic molecules. Present in most cell types in all eukaryotes. Very high internal enzyme concentration sometimes ------------

Peroxisomal proteins use a peroxisomal targeting signal (PTS), e.g. PTS1 signal is (------)-Lysine-Leucine, and transport directly into peroxisomes in a ------ state