[FMS] CBS - protein structure + function Flashcards
At physiological pH what is ionised?
- Asp and Glu carboxyl groups are ionised – COO-
- Lys and Arg amino groups are ionised – NH3+
5 features of a peptide bond
What are 2 clinical conditions that are a result of defects in metabolism?
Phenylketonuria (PKU), defective
phenylalanine hydroxylase (phe→tyr) resulting in reduced tyr production and hormones that are
derived from it
Albinism (many forms) one form due to defective tyrosinase
(tyr →melanin)
what molecule does the first amino acid have and which end is it found?
First aa has NH3⁺ group
N-terminal end
NH3+ = N terminus
COO- = C terminus
what molecule does the last amino acid have and which end is it found?
Last aa has COO⁻ group
C-terminal end
what are the 2 Post translational covalent modifications?
- Disulphide (S-S) bridges between two cys
Joining subunits together e.g. insulin - Glycosylation
O-linked -OH of thr and ser
N-linked -NH2 of asn
^ remember:
diSulphide= S-S
glycosylatiON =O/N linked
O=OH
N= AsparagiNe
what are the 4 levels of 3D structure
Primary – sequence of aa in peptide chain
Secondary – folding/coiling of peptide chain (usually into a α-helix or β-pleated sheet)
Tertiary – peptide chain folds upon itself
Quaternary – folded peptide chains join together
what bonds is the alpha helix formed by in the same polypeptide chain?
formed by H-bonds in same polypeptide chain (backbone not side chains)
where do the h-bonds in alpha helixes form?
H-bonds formed between the amino and carbonyl groups of every fourth peptide bond.
is the alpha helix regular or irregular, and is it right or left-handed?
regular, right-handed helix
remember alpha helix is RR = regular righthanded
whats the residue number for an alpha helix and how are the turns stabilised?
3.6 residues/turn stabilised by H-bonds
are the r groups on the inside or outside of an alpha helix?
R groups on the outside
what kind of shape does an alpha helix have and why?
rigid cylinder shape, acts as ‘architectural’ support for protein
what kind of peptide chains are b-pleated sheets made from?
Linear peptide chains
what kind of bonds hold the sheets together in b-pleated sheets?
H-bonding between peptide chains holds strands together in a β-sheet
where do the side chains lie in a b-pleated sheet?
Side chains in each strand alternately lie above and below the plane of the sheet
what 2 forces stabilise protein structure?
covalent
non covalent
give an example of a specific covalent force that stabilizes protein structure?
Covalent:
Disulphide bridges (not all proteins have them)
give examples of 4 specific non-covalent forces that stabilizes protein structure?
Non–covalent:
Hydrophobic effect
Hydrogen bonds
Electrostatic interactions
Van der Waals forces
REMEMBER: HHEV
what are the 2 types of b-sheet structures?
how many chains is a collagen helix made up of?
3
what kind of bonds are between collagen triple helix
h bonds
how many residues are there in collagen triple helix
3
is a collagen triple helix right or left handed?
left handed helix
which protein has a high % of b sheets
Fibrillar proteins
silk fibres (fibroin)
properties of high tensile strength, but no elasticity
why are there hydrophobic regions in a protein?
Hydrophobic regions of a protein fold in such a way to minimise the contact with aqueous environment.
Hydrophobic regions are unable to form hydrogen bonds
what 3 things can proteins be denatured by?
heat, detergents, pH
what disease arises from the mutation of a protein?
mutation = misfolding
e.g SICKLE CELL DISEASE
GLUTAMIC ACID to VALINE at position 6 on globin surface.
Glu is hydrophilic and negatively charged, Val is hydrophobic.
Stabilises polymerization of HbS.
what 2 diseases arise from stable aggregation of proteins
Amyloid proteins forming plaques in Alzheimer’s Disease (aggregation of misfiled proteins)
Prion protein polymerisation in Creuzfeldt-Jakob Disease
REMEMBER:
Amyloid = Alzheimers
Prion = CJD
whats the disease called when theres defects in metabolism that result in reduced tyrosine production and hormones derived from it?
Phenylketonuria (PKU), defective
phenylalanine hydroxylase (phe→tyr) resulting in reduced tyr production and hormones that are
derived from it
whats the disease called when theres defects in metabolism that result in defective tyrosinase
Albinism (many forms) form due to defective tyrosinase
(tyr →melanin)
what are the 4 structural features of lysozymes
What is X and Y in this sequence: - Gly - X - Y - Gly - X - Y - ?
X = mainly proline
Y = mainly hydroxy-proline
Where are electrostatic interactions found?
Between charged side chains
what is the structure of a protein determined by?
sum of multiple low energy bonds - The amount of stablization energy in a protein is quite small
What do amino acids encode in addition to the final protein structure
Amino acid sequence encodes the final structure but also the pathway that leads to that structure
