2.16 Protein Processing Flashcards
Portions of a nonfunctional protein are removed, resulting to release of an active protein
Cleaving
Responsible for removing these portions by breaking their peptide bonds
Endoproteases
Inactive precursors of enzymes
Zymogens
inactive form of trypsin
Trypsinogen
Inactive form of chymotrypsin
Chymotrysinogen
Inactive precursors of hormones
Prohormones
Covalent attachment of chemical groups to protein
Altering
Modifications by altering include:
Phosphorylation
Glycosylation
Hydroxylation
Other covalent modifications (Carboxylation and Farnesylation)
Addition of phosphate groups by kinases
Phosphorylation
Occurs on hydroxyl groups of serine, threonine and less frequently in tyrosine
Phosphorylation
Addition of carbohydrate to form glycopreoteins
Glycosylation
Important in producing antigenic properties of proteins
Glycosylation
Used for protein targeting and signaling
Glycosylation
Addition of hydroxyl groups by hydroxylases
Hydroxylation
Glutamate residues are carboxylated to become gamma-carboxyglutamate
Carboxylation
Attachment of lipids for anchoring proteins to membranes
Farnesylation
Proteins that are aberrant are tagged for destruction
Degrading
Located almost everywhere in the cell and tags aberrant proteins
Ubiquitin
Destroys abberant proteins
Proteasome
Enzymes hydroxylates and oxidizes specific AA (proline, lysine)
Amino terminal peptides are cleaved off
Procollagen
Multiple ribosome units are translating the same mRNA
Polyribosomes/polysomes
Polysomes are located in ___ or within ___
Cytosol
RER
Protein sorting occurs via two pathways:
Cytosolic pathway
Rough endoplasmic reticulum pathway
Proteins for the nucleus, peroxisome, mitochondria, cytosol
Cytosolic pathway
Membranes, lysosomic enzymes, secretory proteins
RER pathway
Signal sequences produced in initial translation will determine if the protein will be fully synthesized in free cytosol or rough ER
Signal Hypothesis
Components of signal hypothesis
Signal sequence Signal recognition particle SRP receptor Translocator Signal peptidase
Ribonucleoprotein that consists of a 7s RNA with 300 nucleotides and 6 different proteins
Signal recognition particle
Nuclear localization proteins
Nucleus
Peroxisomal-matrix targeting sequences
Peroxisome
Targeting proteins to the matrix
Mitochondria
RER pathway
Membranes (Plasma, ER, BGA)
Lysosomes
Secretory proteins
Pancreatic cancer cells
Zymogens
Pancreatic beta cells
Insulin
c-Peptide
Amylin