Lecture 6 Flashcards
Protein Structure and Protein Folding
What is a supersecondary structure?
Elements of a secondary structure (helices and strands) connected by turns or regions of less ordered structures (loops/coils)
What are the examples of common supersecondary structures?
Helix - turn - Helix
Beta hairpin
Greek key
Strand - helix - strand
What are examples of helix - turn - helix
DNA binding proteins and Calcium binding proteins
Describe a beta hairpin
Common, antiparallel beta strands, variable length
What is a greek key?
Four antiparallel beta strands
What are protein domains?
Elements of supersecondary structures combined where independently folded regions often possess specific functions within the protein
What is the arrangement of elements within protein domains?
Arranged into a hydrophobic core and hydrophilic exterior for stability
What are the three tertiary protein domains?
Alpha domain family
Alpha/beta family
antiparallel beta family
What are examples of the alpha domain family?
Four helix bundle and Globin fold
Describe a four helix bundle
Four helices with three turns arranged to to form a hydrophobic core
Describe the globin fold
Amphipathic helices with side-chains packed closely together within a hydrophobic core, packing can occur between nonadjacent helices
What are examples of the alpha/beta family? (3)
alpha/beta barrel, alpha/beta open twisted sheet, alpha/beta horseshoe fold
Describe the alpha/beta barrel
alternating alpha helices and beta strands connected with loops and arranged so the hydrophobic core is deep within the barrel
Describe the alpha/beta horseshoe fold
16 strand, helix motif repeats
What is an example of the antiparallel beta family?
The anti-parallel beta barrel
What is the arrangement of the anti-parallel beta barrel?
A hydrophobic core and hydrophilic exterior
What is the function of the anti-parallel beta barrel?
Retinal binding
How are proteins synthesised?
As linear polymers that fold into a 3D functional structures
Where are proteins made?
At the ribosomes
How do proteins fold?
Spontaneously through their amino acid structure acting as the instructions
What is the Anfinsen experiment
Where the protein was unfolded and denatured to remove any ribosomes or extra cells to determine that they fold spontaneously
What is the protein folding pathway?
- Formation of short secondary structure segments
- Subdomains form
- Subdomains come together to form a partly folded domain - ‘molten globule’
- Final domain structure emerges, small conformational adjustments to give final compact native structure
What stabilises protein folding?
Non-covalent interactions e.g. H-bonds, metal bonding, disulfide bonds, salt links, hydrophobic core
What are chaperones?
Structures that assist in protein folding
