BCHM - Functions and Dysfunctions of Protein Processing Flashcards
In the cytoplasmic pathway of protein sorting, where are the proteins destined for?
Cytosol, mitochondria, nucleus, and peroxisome
In the cytoplasmic pathway of protein sorting, where does protein synthesis begin and end?
Begins and ends on the free ribosomes of the cytoplasm
In the secretory pathway of protein sorting, where are the proteins destined for?
Endoplasmic Reticulum, lysosomes, plasma membrane, or secretion
In the secretory pathway of protein sorting, where does translation begin and end?
Begins on free ribosomes, but ends in ribosomes sent to the ER
Proteins undergo second part of synthesis in the ER
Have ER targeting signal sequences on first 20 amino acids (N-terminus)
In the cytoplasmic pathway, what signal moves the protein to the cytoplasm?
No signal required
In the cytoplasmic pathway, what signal moves proteins into the mitochondria?
N-terminal hydrophobic alpha-helix
In the cytoplasmic pathway, what signal moves proteins into the mitochondria?
N-terminal hydrophobic alpha-helix
In the cytoplasmic pathway, what signal moves the protein into the nucleus?
Lysine and Arganine rich signals
In the cytoplasmic pathway, what signal moves the protein into the peroxisome?
Serine, Lysine, Leucine signaling complex
In the secretory pathway, what moves the protein into the ER?
KDEL
Lysine, aspartic acid, glutamic acid, and leucine
In the secretory pathway, what moves the protein into the cell membrane?
N-terminal apolar signals
Examples include GLUT transporters
In the secretory pathway, what moves the protein into the lysosome?
Mannose-6-phosphate
In the secretory pathway, what moves the protein into a secretory vesicle for secretion?
Trp-rich domains
Tryptophan
During the import of mitochondrial proteins, HSP70 does what?
HSP70 is a chaperone protein that protects the mitochondrial protein from degradation
Describe the pathway of mitochondrial protein import
Proteins pass through TOM and then TIM. After that, they enter the matrix, and a peptidase cleaves the signaling sequence, trapping the protein within the mitochondrial matrix
Describe the pathway of nuclear protein import
- Proteins pass through nuclear pores
- Small proteins can pass through un-aided, but larger proteins (>40 kDa) require nuclear localization signals
- four continuous basic residues (Lys and Arg)
During the secretory pathway, the signal recognition particle does what?
Binds to the ER-targeting signal and the ribosome during translation. It then wraps itself around ribosome-mRNA-peptide complex, tethering it to the ER membrane, thus halting its translation temporarily
What is Inclusion Cell Disease?
A disease characterized by a defective or missing GlcNAc phosphotransferase, and enzyme that adds M6P to lysosomal hydrolases.
No M6P tagged on lysosomal proteins
If the enzymes are not phosphorylated, they cannot be sorted into vesicles and delivered to lysosomes
Describe the clinical presentation of Inclusion Cell Disease
Failure to thrive, developmental delays, and physical manifestations such as hepatosplenomegaly and defective heart valves.
Death frequently occurs by age 7 due to congestive heart failure or recurrent respiratory tract infections
What is the function of chaperone proteins?
To protect large proteins and help fold into proper tertiary structure