Protein structure Flashcards
What are the 3 main weak interactions in proteins?
1 - Hydrogen Bonds
2 - Van der Waals forces (dipoles between charges)
3 - Hydrophobicity
Describe the 4 levels of protein structure.
primary structure - amino acid sequence
secondary - stretches of the amino acid sequence folding up. arrangements of the chain into alpha helices or beta strands
tertiary - collections of linked secondary structure elements fold together in motifs/patterns and these combined form the structure of the complete folded sequence
quarternary - subunits aggregate together top form the biologically active molecule i.e. the Q structure
What is convergent evolution?
implies arrival at the same or similar function and/or structure from different starting points
What is divergent evolution?
implies a common ancestor, the end result of accumulated mutations in either duplicated genes or diverged species usually being a retention of function and usually a reasonable level of sequence and structural homology.
What are the 2 most common tertiary structure motifs, which are termed domains?
alpha-beta domains comprised of a mostly parallel beta sheet flanked by alpha helices
the parallel alpha-beta barrel. a parallel beta barrel surrounded by alpha helices
How is the tertiary structure stabilised?
soluble proteins are in their most stable state in water and are stabilised by weak forces such as H bonds, VDW and hydrophobic forces
other forces that stabilise include ionic electrostatic bonds/salt bridges between charged side chains, and disulphide bridges which are formed from the oxidation of 2 cysteine side chains
What does homology mean?
the term used to describe the similarities in sequence or structure between 2 or more proteins or genes
What methods are there for determining protein structure?
1 - xray crystallography
2 - high resolution electron microscopy
3 - nuclear magnetic resonance
