Protein Structure Part 2 Flashcards
What is Cysteine and what is it responsible for ?
Cysteine, an amino acid containing a thiol group, is responsible for the disulfide bonds that hold a tertiary structure together. In the tertiary structure, when two helices come together, they may be linked by these disulfide bonds.
While tertiary structures that contain more crossed disulfide bonds, formed by cysteine residues, lead to stronger, stiffer and harder structures such has exoskeletons. Others examples of protein that contain more disulfide bonds include claws, nails, and horns.
What do Tertiary Structures with fewer disulphide bonds do ?
form less rigid structures that are flexible, but still strong and can resist breakage such as hair and wool.
While tertiary structures that contain more crossed disulfide bonds, formed by cysteine residues, lead to stronger, stiffer and harder structures such has exoskeletons. Others examples of protein that contain more disulfide bonds include claws, nails, and horns
What do domains particlaur do and how ?
Some polypeptide chains fold into several compact regions. These regions in a polypeptide chain are called domains and generally range from 30 to 400 amino acids.
On average, domains contain roughly 100 amino acids.
Each domain forms its own tertiary structure which contributes to the overall tertiary structure of the protein. These domains are independently stable.
Stabilization is caused by metal ions or disulfide bridges that cause the folding of polypeptide chains.
Different proteins may have the same domains even if the overall tertiary structure is different.
There are four types of domains:
All-α domains - Domains made purely from α-helices.
All-β domains - Domains made purely from β-sheets.
α+β domains - Domains made both of α-helices and β-sheets.
α/β domains - Domains made from both α-helices and β-sheets layered in a β,α,β fashion with a α-helix sandwiched in between 2 β-sheets.
How is Tertiary Structures determined which method?
determined through X-Ray Crystallography and Nuclear Magnetic Resonance (NMR) Spectroscopy.
X-ray crystallography is one of the best methods because the wavelength of an x-ray is similar to that of covalent bonds found throughout proteins, creating a clearer visualization of a molecule’s structure.
The scattering of x-rays by electrons is analyzed to determine the structure of proteins. In order to use x-ray crystallography, the protein in question must be in crystal form. Some proteins crystallize readily, while others do not. For those proteins that do not crystallize readily, nuclear magnetic resonance (NMR) spectroscopy must be used to determine its structure.
NMR spectroscopy uses the spin of nuclei with a magnetic dipole and chemical shifts to determine a molecule’s relative position.
Give an example of a Quaternary Structure ?
Haemoglobin is one of example of quaternary structure.
HEMOGLOBIN: the oxygen-carrying protein in blood, consists of two subunits of one type (designated alpha) and two subunits of another (designated beta).
What are Quaternary Structures ?
A quaternary structure refers to two or more polypeptide chains held together by intermolecular interactions to form a multi-subunit complex.
The interactions that hold together these folded protein molecules include disulphide bridges, hydrogen bonding, hydrogen bonding interactions, hydrophobic interactions interactions and London forces.
These forces are usually conveyed by the side chains of the peptides
Polypeptide subunits interact through non-covalent bonds to form one functional proteins
What about the peptide of the structure ? In terms of Identical
The peptides of the protein can be identical or different. Insulin is a dimer consisting of two identical peptides, while Haemoglobin is a tetramer consisting of two identical alpha subunits and two identical beta subunits.
Give an examples of Quaternary Structure ?
Collagen a fibrous protein which has three identical helical polypeptide tissue in tendon ,skin and ligaments other body parts
Roles of Proteins
Catalysing chemicals such as enzymes
Cell signalling -Hormones controlling specific processes ,growth, development and metabolism
Antibodies can act as protein by recognising foreign agents such as bacteria and group to remove them.
When does Denaturation occur ?
When a protein unfolds loosing its higher order but not it sequence do to being stronger .
What are Aliphatic ?
non-polar,
Hydrophobic
Alanine, valine , leucine and isoleucine
Stabilizing protein with hydrophobic .
Glycine Grouped/Structure ?
its grouped with non-polar groups its simplest structure
With a H group no real contribution by hydrophobic effect.
Methionine , slightly non-polar
Proline; aliphatic side chain with distinctive cyclical structure rigid reducing flexibility .
Aromatic R group (Properties)
They have unique properties although they are non-polar and contribute to hydrophobic effect .They include phenylanine,tyrosine and trypotan.
Tyrosine /tryptophan OH can form hydrogen bonds .Its important in functional groups in enzymes .
Howver, trysoine and trpptan are more polar than phenalnine because of the hydroxyl group of tyrosine
Nitrogen of indole ring trptopton .
What about positively charged (Basic ) R group ?
+/- charged
pH 7
Lysine,histidine,
Serve as acceptors , portons and donors
What about negative charged (Basic) R group ?
R groups Negative charged Charge of pH 7 Asparte /glutamate Second Carboxyl group
