Amino Acids and Protein Structure Flashcards
Components of AA
C, carboxylic acid, amino group, H
Nonpolar Amino Acids
in interior of soluble proteins and membrane associated proteins to interact with nonpolar fatty acids
hydrophobic clumping contributes to stability of structure
Maple Syrup Urine Disease
defective breakdown of branched chain aa (Isoleucine, leucine, valine)
Neurotoxicity can lead to mental retardation
Treated with diet low in those aa
Phenylalanine
Nonpolar converted to tyrosine during catabolism defect in this causes PKU neurotoxicity causes retardation treatment is diet low in Phe
Tryptophan
Nonpolar
precursor for serotonin, which is a neurotransmitter for pain, sleep, appetite, temp, bp, mood
Glycine
Nonpolar
Collagen = Gly-X-Y
Oseogenesis imperfecta
normal collagen structure disrupted by switching glycine for another aa
can cause death in utero or multiple fractures at birth
Proline
Nonpolar
rigid structure around A carbon
special structural roles in some proteins, and can interfere with formation of some structures
Methionine
Nonpolar
Methyl group donor in methylation reactions
Polar Amino Acids
R-Groups participate in H or ionic bonds- interact with each other, aqueous environment, other proteins
Acidic Amino Acids
Aspartate and Glutamate
each gives -1 charge in polypeptide
Basic Amino Acids
Lysine and Arginine
each gives +1 charge to polypeptide chain
Histidine
basic aa, but does not count toward charge of polypeptide
can affect pKa of weak acids or bases
carries partial positive charge in hemoglobin
Phosphorylation of Hydroxyl Groups
on Serine, Threonine, Tyrosine (polar uncharged)
contributes to activity of enzymes or in signal transduction
Disulfide Bonds
2 Cys residues (Polar Uncharged)
contribute to strength of structure
Asparagine
Polar Uncharged
amide group can form N linkage in glycosidic bonds
Serine and Threonine
Hydroxyl group can form O linkage in glycosidic bonds
Glycoprotein Functions
cell surface recognition
cell surface antigenicity
extracellular matrix
Mucins (glycoproteins that protect digestive tract)
Histones
(-) DNA binds to (+) histones with Lys and Arg
Histidine
precursor for histamine
Histamine
messenger that mediates gastric acid secretion and allergic and inflammatory response
Tyrosine
precursor for catecholamines (dopamine, epinephrine norepinephrine)
Defects of protein folding
genetic mutations
age related cellular inefficiencies
environmental/ nutritional abnormalities
ischemia/ reperfusion
Peptide Bond
between carboxyl group and amino group
polar nature makes A Helix and B Sheets possible
