Levels of Protein Structure Flashcards
The SEQUENCE of AMINO ACIDS linked by the peptide bonds; information; determines the overall shape, function and properties
Primary Structure
In sickle cell hemoglobin, what replaces what which causes the error?
Valine (Hydrophobic amino acid) replacing a glutamic acid (negatively charged amino acid
Amino acid sequencing steps (3)
- Hydrolysis - affected by acid, alkali, or enzyme
- Identification of the products of hydrolysis
- Fitting the pieces together as in a jigsaw puzzle
Determination of the N-terminal amino acid (2)
A) Sanger’s method (2,4 - dinitrofluorobenzene)
B)Edman degradation (PITC, phenylisothiocyanate)
Determination of the C-terminal amino acid (2)
Carboxypeptidase A - cleaves peptide bonds w? AROMATIC amino acid
Carboxypeptidase B - cleaves basic amino acid residues
Used to cleavage the polypeptide into fragments (4)
Trypsin - most reliable, cleaves peptide bonds on the carboxyl side of arg and lys
Chymotrypsin - Cleaves peptide bonds on the carboxyl side of phe, tyr, and trp
Pepsin - cleaves peptide bonds at amino end of AROMATIC and ACIDIC amino acids
Cyanogen Bromide - CNBr cleaves peptide bonds on the carboxyl side
DNFB
tags the amino end (start), becomes DNP
Carboxypeptidase A and B
cuts the carboxyl end (right)
Trypsin
Arg Lys
Chymotrypsin
Phe Tyr Trp
Pepsin
Amino end of aromatic and acidic amino acids
The primary sequnce of a protein, chain of covalently linked amino acids, folds into regularly repeating structures that resemble designs in tapestry
results of hydrogen bonding between the amide hydrogens and the carbonyl oxygens of the peptide bonds
Secondary structure
Most common type of secondary structure
Adopts a shape like a coiled spring
alpha-helix
Parallel - chains run in the same direction, N terminals head to head
Antiparallel - chains run in the opposite direction; more stable N aligned to C
Beta-pleated Sheet
Formed when two polypeptide chain segments line up side by side
Parallel - chains run in the same direction, N terminals head to head
Antiparallel - chains run in the opposite direction; more stable N aligned to C
Beta-pleated Sheet
Proline and Glycine are prevalent in beta turns (why?)
Pro is able to adopt cis conformation like the glycine
Results from interactions between amino acid side chains separated from each other
Defines biological function of proteins
Fibrous - mechanical strength, structural components
Globular - transport, regulatory, enzymes
Tertiary Structure
Strong between two cysteine groups; strongest of the tertiary bonds
Disulfide bond
Salt bridges between charged side chains of acidic and basic amino acids
Electrostatic interactions
Between polar acidic and basic R groups, must be attached to O, N or F
H bonding
Between non-polar side chains
Hydrophobic interactions
Quarternary structure which is a protective coating for organs, major constituent of hair, mainly hydrophobic
determined hardness from S-S bonds, becomes more brittle
Alpha-Keratin (fibrous)
Quarternary structure which is the most abundant protein in humans, Organic component of bones and teeth
Rich in proline
Collagen (fibrous)
Quarternary structure Oxygen storage molecule, higher oxygen affinity than hemoglobin
Reserve oxygen source for working muscles
Myglobin (Globular)
