One gene, many proteins Flashcards
post-translation modification
After translation, the nascent polypeptide chains are:
1) folded and a cofactor binds to it
2) covalent modification by glycosylation, phosphorylation and acetylation,…
3) binds to other protein subunits
becomes a mature functional protein
molecular chaperones
a protein complex helping the PTM to occur on newly made polypeptide chains
phosphorylation
What: addition of a phosphate group to specific amino acid residues
How: catalyzed by kinases protein transferring phosphate from ATP to the amino acid
acetylation
What: addition of an acetyl group to a lysin residue
How: acetyltransferase transfers the acetyl group from acetyl-CoA to the ε-amino group of lysine
ubiquitination
What: attachment of ubiquitin molecule to lysin residue
How: Ubiquitin ligases transfer ubiquitin to the target protein
Methylation
What: Addition of a methyl group to an amino acid
How: catalyzed by methyltransferases
glycosylation
What: attachment of carbohydrates (sugar) molecules to amino acids
How: glycosyltransferases
dissulfate bond formation
What: Covalent linkage between two cysteine residues via a sulfur-sulfur bond (-S-S-)
How: Oxidation of cysteines leads to disulfide bond formation. Disulfide bonds stabilize protein structures, especially in extracellular proteins.
carbonylation
What: addition of carbonyl group to amino acids
How: Oxidative stress induces carbonylation, leading to protein dysfunction and potential degradation.
signal peptide
If the polypeptide is designed for the endomembrane system, there is an addition of a sequence of about 20 amino acids at or near the leading end (N-terminus) of the polypeptide
signal-recognition particle (SRP)
recognizes the signal peptide and guides the ribosomes to a receptor protein on the membrane of the ER
transcriptional control
enzymes connect to the histone tails and acetylates it to open the the chromatin structure and promote transcription.
other enzymes methylate the DNA part that is not transcribed often
Activator and repressor proteins initiate and regulate the transcription
translation control
the initiation can be blocked by regulatory proteins binding on the untranslated region preventing ribosomes from attaching.
mRNA degradation control
it can survive for hours, days and weeks and be stored
untranslated 3’ of the molecule have a specific sequence to affect the longevity of the mRNA
protein activity control
activated by the addition of a phosphate group
ubiquitin attaches when the protein must be destructed
