Post Translational Modifictations Flashcards
Glycosylation
Happens on extracellular proteins that will be covalently linked to sugar residues on the ER lumen. O-links are formed with the hydroxyl group of SER or Thr residues.
N-linked occur on asparagine residue
Phosphorylation
Ester bond between phosphate and OH of an amino acid.
Serine/threonine and tyrosine kinase help achieve this.
Regulates enzyme activity and protein function
Disulfide bond formation
Inter and intra molecular disulfide bonds between thiol group of 2 cysteine residues will stabilize proteins. Formation occurs in the ER lumen, facilitated by protein disulfide isomerase
Acetylation
Lysine residues are acetylated by acetyl coA group donors.
Collagen modification
Modifications are important for assembly of collages.
Ascorbic acid is essential fo activity of Lysol and prolly hydroxylases. Defects in lysyl hydroxylases will result in skin, bone, and joint disorders
Alzheimer’s disease
Amyloid precursor protein will break down to form amyloid beta peptide. Misfolding or aggregation of this forms a plaque (extracellular)
Hyperphosphorylation of Tau will lead to neurofibrillary tangles (intracellular)
Parkinson’s Disease
Aggregation of a-synuclein will cause insoluble fibrils that will deposit as Lewy bodies in dopaminergic neurons in the substantial nigra, reducing availability of dopamine
Huntington’s Disease
A Huntington gene mutation will result in expansion of CAG triplet repeats. This results in polyglutamine repeats in the HTT protein. They will form intramolecular H bonds that will misfold and aggregate
Symptoms caused by cell death in basal ganglia
Creutzfeldt-Jakob disease
A misfolding of prion proteins will spread to healthy proteins so that all proteins will be misfolded. Results in spongiform - filled with holes, resembling sponge
