Protein function and synthesis Flashcards
Glycosylation
covalent addition of sugar moietites to proteins which is required for their function and/or cellular localization
Glycation
Covalent addition of aldose or ketose to proteins resulting in advanced glycated end (AGE)-modified proteins via Maillard/Amadori reactions
-associated with alterations of protein properties during aging and diabetes
Sulfation
Transfer of a sulfate group on TYR from the universal donor PAPS catalyzed by Tyrosylprotein Sulfotransferase
-Role: secretion of various endocrine peptides gastrin, CCK, calcitonin
Phosphorylation
Addition of a phosphate group
-serine/threonine phosphorylation
-Tyrosine Phosphorylation
Role: rapid regulation of protein activity, protein movement and localization, protein-proteins interaction: enzyme, transcription factors, translocation factors, receptors, transporters, carriers, signaling factors
Prenylation
Transfer of farnesyl or geranyl group on a cystein residue present in the CAAX consensus sequences
Role; targeting and anchoring proteins to membrane
Fatty Acylation
Transfer of palmitate on Cys residues with the formation of a thioester bound (reversible/irreversible) and transfer of myristate on G residues with the formation of an amide bond (irreversible)
ROle: targeting and anchoring proteins to membrane
Describe the ubiquitination process
- Attachment of activated ubiquitin by E1, a subunit of ubiquitin enzyme system, which hydrolyzes ATP to form a thiol ester with the carboxy end of ubiquitin. This activated ubiquitin is transferred to another protein, E2, referred to as ubiquitin-conjugating enzymes
- The carboxy end of ubiquitin is ligated by E3 to a protein substrate that is ultimately to be degraded. E3 has two distinct sites that interact with a targeted protein’s N terminal amino acid
List the four ways proteins synthesis is regulated
- Hormonal effects
- Slow vs Fast proteins
- Plant vs animal proteins
- mTOR regulatory mechanisms
How does insulin and growth hormone affect protein
- Insulin: increases with feeding, stimulates synthesis of protein and inhibits protein degredation, regulates imitation and translation of mRNA by regulating phosphorylation of imitation factors
- Growth hormone: long term regulation of growth, causes production of insulin like growth factors of -1 and 2 by liver and other tissues to regulate specific proteins
How does testosterone affect protein
promotes protein synthesis in muscle by regulation transcription
How do stress hormones affect protein
catabolic in nature
Cortisol and glucagon can ____ protein synthesis
inhibit
Higher glucagon levels in liver facilitate synthesis of ____ ____ involved in ____ and ______
higher glucagon levels in liver can facilitate synthesis of hepatic enzymes involved in gluconeogenesis and ureagenesis
Increase in cortisol promote muscle protein catabolism to
shuttle AAs for gluconeogenesis
Slow vs fast proteins affect
-digestion and absorption
-rate of appearance of AA in plasma
-subsequent utilization of AA within cells
Fast protein
Whey, soy, AA mixtures, protein hydrolysates
-better stimulates MPS and whole body protein synthesis at rest and following resistance training
Slow protein
casein- lower and more prolonged plasma AA concentrations - reduce protein breakdown
Plant vs animal protein
-Animal proteins higher in Leucine (greater stimulation of MPS
-postprandial concentrations of AA that do not contain all essential AA thought to reduce AA availability to tissues, stimulate hepatic oxidation of AA, stimulate ureagenesis
mTOR
mammalian target of rapamycin
-large proteins kinase complex that functions in many cellular protein processes involving cell growth/proliferation
-amino acids (leucine and arginine) participate in regulation of mTOR activity which in turn regulate protein synthesis
List out protein functions
- catalysts (enzymes)
- Messengers
- structural elements
- buffers
- Fluid balancers
- immunoprotectors
- Transporters
- Acute phase responders
- Cell adhesion, conjugated proteins
