Protein structures Flashcards
What type of reaction is the formation of a peptide bond? What does it require?
endothermic reaction requiring ATP
What is a Zwitter ion?
where 2 groups of an amino acid have an opposite charge, creating an overall neutral charge
What is the importance of knowing about protein structure?
-to interpret the structural basis for protein function
-to predict protein-protein interactions
-aid in rational drug design
What are 2 major techniques used to solve protein structures?
-X ray crystallography
-Nuclear Magnetic resonance (NMR).
Define Globular proteins
Give an example
proteins with transmembrane domains consisting of alpha helices or beta-barrels
E.g.) ompF porin
Define Fibrous proteins
Give some examples
Structural proteins consisting of different polypeptide chains
E.g.) Collagen, Keratin, Actin, Tropomyosin
What is the hierarchy of protein structure?
-Primary
-Secondary
-Tertiary
-Quaternary
What is the primary structure of a protein?
the order of amino acids in the protein from the N-terminus to the C-terminus
What are the characteristics of a peptide bond?
-partial double-bond character
-no rotation can occur around it
-planar (flat).
What type of interactions stabilise protein structure?
- Hydrophobic interactions
-Hydrogen bonds
-Ionic interactions
-Disulphide bridges - Pi stacking
What is an a- helix?
-common secondary structure stabilised by hydrogen bonds between the oxygen and amide nitrogen 4 residues later
How many residues occur per turn of an alpha helix?
3.6
What are B-sheets?
Secondary structures that can be parallel or antiparallel, formed by hydrogen bonds between backbone atoms of different strands
Super-Secondary structure: What are structural motifs? Give 3 examples
specific combinations of secondary structure elements often seen in protein structures.
E.g.)
-Four helix bundle
- Greek Key
-TIM barrel
What is the tertiary structure?
-the overall 3D structure of a single polypeptide chain
-regions of a protein can twist /bond independently
What is Quaternary structure? Give an example
The structure formed by more than one polypeptide chain
E.g.) Haemoglobin has 2xa and 2xB subunits
How do proteins fold into the correct structure?
-all information for correct folding is present in the sequence of amino acids.
-Proteins undergo post-translational modifications
What happens if proteins misfolding occurs?
-can lead to loss of function, disease
-in some cases infectious properties
What do cells do to ensure correct protein folding?
-use chaperone proteins and other mechanisms to ensure correct folding and prevent misfiling
Name a Secondary structure that contains only B-pleated sheets
OmpF porin
Name a Secondary structure that contains only Alpha- helices
Myoglobin
Name a Secondary structure that contains both alpha and beta chains
Lipase, Tyrosine kinase
Alpha-helices are often______
amphipathic
What is the advantage of X-ray crystallography compared to NMR?
has a higher resolution and is able to look at larger proteins
