Session 4.3a - Lecture 1 - Protein Structure Flashcards
Slides 1-11
ILO
- What do proteins do
- Structural aspects
- Think about how some of these things fit together and work
- E.g. enzymes
Do NOT need to know all the molecular detail of the DNA repair pathways
Steve Foster lectures
What was the take home message from SF lectures?
There are many different types of DNA repair mechanisms
Why do we need many different types of DNA repair mechanisms?
Because DNA repair is very important; if things go wrong with DNA we need to put them right
What can occur if DNA is damaged and not repaired?
If there are changes, that will affect DNA and therefore the function of the cell, so it is critically important to have DNA repair mechanisms
Why do we need to know about DNA repair mechanisms?
We need to UNDERSTAND the importance of their role, as if DNA is not fixed then the function of the cell is changed
What is non-homologous end joining (NHEJ)?
NHEJ is joining DNA when there’s a double stranded break.
Need to know BASICS but NOT all the proteins involved
Why can NHEJ go wrong?
Although NHEJ is a neat process that repairs dsbreaks quite nicely, it is NOT very selective. This means that the process can be prone to errors.
What can occur if NHEJ goes wrong?
Translocation events can occur.
What are the levels to proteins?
Primary
Secondary
Tertiary and
Quaternary structure
What are proteins made up from?
Amino acids
How do proteins differ?
Although they are all made up from amino acids joined together, these tend to FOLD UP in different ways
What is the primary structure of a protein?
Just the amino acids joined together
What is the secondary structure of a protein?
The localised folding of the amino acid sequence
What is the tertiary structure of a protein?
When the protein is folded up as a whole
What is the quaternary structure of a protein?
When more than one subunit comes together to form a protein
Fig. 2
Label the image
Left - proteins crystals used to get 3D structure of proteins
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
What is the relationship between protein structure and function?
Proteins fold up in different ways (due to their amino acid sequence) which relates to their function
Why do we need to know about proteins, why are they important?
Proteins play crucial roles in virtually all biochemical processes - they do virtually everything in your cell that is of any consequence.
What is the difference between DNA and protein?
DNA carries all the information but it’s the proteins that do things.
What are the functions of proteins that are important in medicine?
- Catalysts
- Transporters
- Structural support
- Machines
- Immune protection
- Ion channels
- Receptors
- Ligands in cell signalling
What is an example of proteins as catalysts?
Enzymes
What are enzymes an example of?
Catalysts
What is virtually every enzyme?
A protein (there might be other things associated with it but virtually all enzymes are proteins).
Give 2 examples of things proteins can transport
Oxygen and iron
Other than oxygen and iron around the body, where else can proteins transport things?
Things across cell membranes
What is the support in the body?
All support in body is really protein-based
What is an example of structural support in the body from proteins?
Collagens in skin and bone
What are the proteins found in bone, skin etc. that function as structural support?
- Collagen
- Other scaffolding proteins
How do proteins act as molecular machines?
In muscular contraction and motion
What are the protein elements involved in muscles?
Actin and myosin
Where are actin and myosin found in muscles?
In sarcomeres
What is a sarcomere
The basic unit of striated muscle tissue.
How do proteins function for immune protection?
Immunoglobulins
What type of immunity is due to proteins?
Virtually all adaptive immunity down to role of proteins
What is the role of immunoglobulins?
Recognise any antigen effectively that comes into your body
What is the significance of proteins being immunoglobulins?
They need to recognise any antigen that comes into your body, which means there must be a huge repertoire of Igs! This can be produced by proteins because there are numerous different ways a protein can fold.
How are proteins important for cell communication?
They can form ion channels, receptors and ligands in cell signalling
What is the common function of ion channels, receptors and ligands?
Cell communication
What is the function of an ion channel?
For example, to set off electrical impulses in neuronal cells
What are receptors used for?
For hormones, neurotransmitters etc.
Give an example of a function of a receptor
Takes signals from outside the cell and passes to inside the cell - important for how you get hormonal regulation, for example.
Give an example of proteins as ligands in cell signalling
Growth factors
How are proteins and ligands interconnected?
Many proteins themselves will act as ligands - e.g. growth factors are protein-based.
What are the key features of proteins?
- Proteins are polypeptides
- The amino acid sequence of a protein is encoded by a gene
- The polypeptide chain folds into a complex and highly specific three-dimensional structure, determined by the sequence of amino acids
- The folding of proteins depends on the chemical and
physical properties of the amino acids - The amino acid sequence of a protein is encoded by a gene
What are proteins?
Polypeptides - they are macromolecules made up of amino acids
What are polypeptides?
Chains of amino acids, aka proteins.
What is a macromolecule?
A big molecule
What is the simple unit of a protein?
An amino acid
What is the relation between amino acid and protein?
The amino acid is the simple repeating unit in a protein
What forms a protein?
Amino acids joined covalently to give the sequence of the protein (like beads on a strong)
How are amino acids joined together in proteins?
By strong covalent bonds known as peptide bonds.
What type of bond is a peptide bond?
Covalent (strong)
Fig. 4 (left)
Label this image
- Monomers
- A linear polymer
What is another word for macromolecule?
Polymer
If a protein is a polymer, what is the monomer?
Amino acid
If an amino acid is a monomer, what is the polymer?
Protein
If a protein is a polymer, what is an amino acid?
Monomer
If an amino acid is a monomer, what is a protein?
Polymer
Fig. 4 (right)
What does this picture represent?
A protein sequence of amino acid, represented via a letter code (like genome sequences).
How are amino acids represented in a code by molecular biologists?
There is a 20-letter code (don’t need to learn)
How is the amino acid sequence of a protein encoded for?
By a gene
What does a gene do in relation to proteins?
Encodes an amino acid sequence of a protein
What determines the amino acid sequence of a protein?
The nucleotide sequence of a gene
What does the nucleotide sequence of a gene determine?
The amino acid sequence of a protein
The amino acid sequence of a protein is encoded by a gene. What does this link?
This is critically important because it links your GENOME (nucleotide sequence) to your PROTEOME (protein sequence).
Define genome and proteome?
GENOME = nucleotide sequence
PROTEOME = protein sequence
Why is it important clinically to understand that DNA (genome) is linked to the protein (proteome)?
If you get a mutation in a GENE, you can affect the PROTEIN.
What is wrong with the beads on a string model of proteins?
Proteins don’t really adopt that conformation - in some cases they do - but in most cases they fold up into a fine 3D structure
What determines the 3D structure of proteins?
The specific amino acid sequence that make up that particular protein
What does the amino acid sequence dictate?
The 3D structure of proteins
What is it about amino acids that affects the individuality of proteins?
The chemical and physical properties of those particular amino acid “residues” that make up a protein actually contribute to the 3D sequence of the protein.
What is the relation between the chemical and physical properties of an amino acid that make up a protein?
The properties of those particular amino acid “residues” (as we call them) that make up a protein actually contribute to the 3D sequence of the protein.
What is important about 3D structure?
3D structure often determines what a protein does.
Describe how amino acids are related to protein function?
The make up of a protein (its specific amino acid sequence) controls overall 3D shape and 3D shape defines its role.
What encodes the amino acid sequence of a protein?
A gene