lec 9- other localization methods Flashcards
how is phagocytosis carried out?
by a few types of cells specialized for uptake of relatively large particles and in mammals is receptor mediated
what does the phagosome fuse with?
it fuses with the lysosome to become a phagolysosome in which the contents are usually destroyed
are peroxizomes organelles?
yes
how do proteins import themselves into the peroxizome?
by an amino acid sequence that acts as the address which is then recognized by the receptors on the organelles outer membrane
what type of transport do the proteins importing themselves into peroxizomes use?
post-translation
what do peroxizomes contain?
contain oxidases (enzymes that use molecular oxygen to remove hydrogen atoms from specific organ substrates in an oxidation reaction that produces hydrogen peroxide)
what uses the hydrogen peroxides in peroxizomes?
catalase (also in the peroxizome), oxidizes other toxic substances or converted to water/oxygen
what else do peroxizomes break down?
the fatty acids, two carbons at a time into acetyl CoA
what do the peroxizomes do by doing a biosynthetic reaction?
do the reaction which is the first step in forming plasmalogens (phospholipid abundant in myelin)
what are the 4 compartments of the mitochondria where proteins can end up?
-outer membrane
-inner membrane
-intermembrane space
-matrix
which 2 compartments has the most proteins?
the inner membrane and the matrix
what parts of the mitochondria have a protein import complex?
outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM)
can the mitochondria also synthesize membrane proteins?
yes
what is the signal sequence for the internal membrane called?
internal targeting sequences, stay as a part of the molecule
where is the signal sequence for the matrix?
at the N-terminus and is removed
what is TOM complex?
Transporter of outer membrane, includes a receptor and a channel
what is TIM complexes?
Transporter of inner membrane
what are the two TIM complexes?
TIM22- for proteins of the inner mitochondrial membrane
TIM23- for matrix proteins
what helps proteins go inside of the matrix?
chaperones
what does the nuclear lamina do?
provides mechanical support and composed primarily of intermediate filaments
how many membranes does the nuclear envelope have?
2 membranes, outer is continuous with ER
how do proteins, mRNA, tRNA, and ribosomal subunits enter and exit the nuclear envelope?
via nuclear pores
what is the nuclear pore complex (NPC)?
key regulator of transport between nucleus and cytoplasm
what is the collective name of 30 proteins that make up the NPC?
nucleoporins
what diffuses through the NPC?
ions, small metabolites and globular proteins up to 40 kD
how are large proteins transported in the NPC?
by mobile active transport proteins
what do the disordered regions of nucleoporins do?
block large molecules
what do nuclear localization signals (NLS) do?
directs nuclear proteins to the nucleus
explain how a protein is imported into the nuceus?
- importin- B binds to importin-A forming a complex which contains a receptor for an NLS on cargo
- importin-A binds to the NLS of the cytoplasmic cargo protein
- the complex with the NLS protein attached enter the nucleoplasm where importin B interacts with Ran-GTP causing importin-B to release importin-A and cargo seperately
- Ran-GTP-importin-B-complex goes back into cytoplasm, where Ran-GTP is hydrolyzed into RAN-GDP causing release of importin-B which allows it to bind to importin-A again to repeat cycle
- importin-A is delivered back into cytosol by a protein called exportin and Ran-GDP goes back to the nucleus where it is converted back into Ran-GTP
how does Ran-GDP turn back into Ran-GTP?
-Ran is a GTPase that converts GTP into GDP and vice versa:
1. the GDP in the GTPase (Ran) is exchaged for GTP with the help of GEF (guanine nucleotide exchange factor)
2. the GTP in GTPase (Ran) is hydrolized into GDP with the help of GAPs (GTPase activating proteins)
when is GTPase on and off?
on with GTP and off with GDP
