3 -The 3-Dimensional Structure of Proteins Flashcards
What does a protein sturcture adopt what specific conformation?
Three-dimensional
spatial arrangement of atoms in a protein
Conformation
Most abundant and diverse macromolecule in
the cell
Proteins
This three-dimensional structure of a protein is called
Native conformation
proteins in any of their functional, folded
conformation.
Native proteins
essential for the biological
function of a protein.
Native conformation
What happens to the proteins of their is loss of structure?
Loss of biological functions
What are the level of protein organization?
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
what level of protein organization is amino acids
Primary structure
what level of protein organization is a-helix
Secondary structure
what level of protein organization is polypeptide chain
Tertiary structure
what level of protein organization is Assemble subunits
Quaternary structure
It refers to the sequence of amino acids in a polypeptide chain (read from the N- to C-terminal end).
PRIMARY STRUCTURE
It determines the native conformation of the peptide/protein.
PRIMARY STRUCTURE
What level of organization is the Spike protein
Primary structure
full name of SARS-CoV-2
Severe acute respiratory syndrome coronavirus 2
It refers to the ordered 3D
arrangements in localized regions of a polypeptide chain (regular folding)
SECONDARY STRUCTURE
Spatial arrangement of the atoms in the polypeptide chain
SECONDARY STRUCTURE
Formed and stabilized by
hydrogen bond between the
amide proton and carbonyl
oxygen
SECONDARY STRUCTURE
Does the primary structure dictates the secondary structure?
Yes
In a secondary structure why is H-bonded arrangment of backbone protein is possible due to free rotation of bonds between?
*α-C and α-N (phi φ)
*α-C and carboxyl
carbon (psi ψ)
What kinds of structure can be found in a secondary structure
- α-Helix
- β-sheet
- Random coil
Spiral structure
SECONDARY STRUCTURE: α-HELIX
Stabilized by intramolecular hydrogen bonds
SECONDARY STRUCTURE: α-HELIX
C=O of each peptide bond is hydrogen
bonded to the N-H of the fourth amino acid
away; there are 3.6 aa/turn
SECONDARY STRUCTURE: α-HELIX
Pitch: 5.4Å
SECONDARY STRUCTURE: α-HELIX
H-bonds are parallel to helical axis
SECONDARY STRUCTURE: α-HELIX
All R groups point outward from helix
SECONDARY STRUCTURE: α-HELIX
Coil of the helix either right-handed (clockwise) or left-handed (counter- clockwise)
SECONDARY STRUCTURE: α-HELIX
Enumerate the CONSTRAINTS TO STABILITY OF HELIX
- Presence of helix breakers
- Electrostatic repulsion (or attraction) between successive charged aa residues.
- Bulkiness (steric strain) between adjacent R-groups
What are the examples of helix breakers
Pro
Gly
(1) the rotation around the N-αC bond is restricted bec it is part of the ring (2)
N has no H to participate in H-bonds
Pro
has more conformational flexibility due to its R-group; it supports other
conformations (e.g. coil or bend)
Gly
what are strong helix formers
Small hydrophic residues like (Ala, Leu)
It is formed when 2 or more polypeptides line up side by side.
SECONDARY STRUCTURE: β-PLEATED SHEET
Stabilized by hydrogen bonds (intrachain or
interchain) of adjacent polypeptide chains
SECONDARY STRUCTURE: β-PLEATED SHEET
Each β-strand (polypeptide chain in β-sheet)
is extended into a zigzag.
SECONDARY STRUCTURE: β-PLEATED SHEET
H-bonds form are adjacent between β-
strands.
SECONDARY STRUCTURE: β-PLEATED SHEET
All R groups extend above or below the sheet
in an alternating up and down direction.
SECONDARY STRUCTURE: β-PLEATED SHEET
Adjacent β-strands can run in parallel or anti- parallel
SECONDARY STRUCTURE: β-PLEATED SHEET
These are non-repetitive
structures.
SECONDARY STRUCTURE: RANDOM COILS
An irregular or unique
conformation
SECONDARY STRUCTURE: RANDOM COILS
Combinations of α and β-strands
SUPERSECONDARY STRUCTURES
What are examples of SUPERSECONDARY STRUCTURES
βαβ unit, αα unit, β-meander and Greek key
repetitive supersecondary structures
Motif
It refers to three-dimensional conformation of the entire polypeptide.
TERTIARY STRUCTURE
Stabilized by numerous interactions
between amino acid side chains.
TERTIARY STRUCTURE
What does a Tertiary Structure contain?
- Covalent bonds (e.g. disulfide bond
between 2 cys) - H-bonds
- Salt bridges (electrostatic)
- Hydrophobic interaction
polypeptide chain arranged in long strands or sheets
Fibrous proteins
What is Fibrous proteins consist largely of one type of structure?
Secondary structure
What is the function of fibrous proteins?
Strucutral (strength and support)
What are examples of fibrous proteins
Collagen and Keratin
Most are water insoluble
Fibrous proteins
polypeptide chain
folded into compact, spherical structure
Globular proteins
What does globular proteins consist of many types of?
seconday structures
They are largely water soluble.
Globular proteins
what is the functions of globular proteins?
Metabolic (catalyctic, transport)
what are some examples of globular proteins
Enzymes and Hemoglobin
It refers to spatial arrangement of
polypeptide subunits.
QUATERNARY STRUCTURE
subunit
monomer
It is formed by the assembly of
individual polypeptides
(subunit/monomer) into a larger
functional cluster.
QUATERNARY STRUCTURE
how is subunits stabilized?
noncovalent interactions
dimer
2 subunits
trimer
3 subunits
tetramer
4 subunits
Glucose Homeostatic Proteins
INSULIN AND GLUCAGON
Control carbohydrate metabolism by binding on specific receptors
INSULIN AND GLUCAGON
Synthesized at the pancreas
INSULIN AND GLUCAGON
what does the pancreas produce?
Insulin
Glucagon
β-cells
Insulin
α-cells
Glucagon
Hormone of nutrient abundance
INSULIN
A protein hormone consisting of two
amino acid chains linked by disulfide
bonds
insulin
86 AA
proinsulin
function insulin
51 AA
29 AA
C peptide
What are major targets for insulin are?
- liver
- Skeletal muscle
- adipose tissue
The net result is fuel storage
INSULIN
A 29-amino-acid polypeptide hormone
that is a potent hyperglycemic agent
GLUCAGON
Its major target is the liver
Glucagon
Glucagons major target is the liver, where it
promotes:
- Breakdown of glycogen to glucose
(glycogenolysis) - Synthesis of glucose from lactic acid
and noncarbohydrates
(gluconeogenesis) - Release of glucose to the blood from
liver cells
Fed state: insulin dominates causes?
Glucose oxidation
Glycogen synthesis
Fat syntheis
Protein synthesis
Fasted stat: glucagon dominates
Glycogenolysis
Gluconeogenesis
Hemeproteins
HEMOGLOBIN & MYOGLOBIN
What is major or role HEMOGLOBIN & MYOGLOBIN
- Hemoglobin: O2
transport
- Myoglobin: O2
storage
O2 transport
Hemoglobin
O2 storage
Myoglobin
it is a Tetramer
Hemoglobin
what is the primary structure of hemoglibin
- α = 141 aa
- β = 146 aa
the is secondary structure of hemoglobin
helical
what is secondary structure of hemoglobin
Helical
What is tertiary structure of hemoglobin
Globular
What is the 4th structure of hemoglobin
4 folded chain in tetrahedral arrangement
aka as antibodies
IMMUNOGLOBULIN
Y-shaped molecule produced by
B-cells during adaptive immune
response
Immunoglobulin
what is immunoglobulin composed of how many sub-units and what are those?
Composed of 4 sub-units
* 2 heavy chains
* 2 light chains
what is immunoglobulin comprised of? (CVH)
- Constant regions
- Variable regions
- Hinge
Antibody that is commonly found in human secretions like tears, mucous and saliva
IgA
Cell attached antibody which functuon is still under study
IgD
Antibody responsible for allergic reactions
IgE
Most dominant antibody in humans. This antibody is responsible for secondary immune response
IgG
The antibody whichh serves as protection for primary infections
IgM
It refers to disruption of the protein
conformation as well as its function
DENATURATION
Alteration in the environment causing
disruption in the bonds and forces of
interaction that stabilized protein
structure
DENATURATION
Enumerate the PROTEIN DENATURATION
- Physical Denaturants (heat)
- Chaotropic Agents (urea, detergents, salts, acids, bases, alcohols)
- Reducing agents (mercaptoethanol)
- Heavy metals
what are urea, detergents, salts, acids, based, alcohols
Chaotropic agents
What does altered protein sequence contain two categories
Normal protein function
Altered protein function