Protein Folding Flashcards
What is the predominant force driving protein folding?
Solvent shielding of hydrophobic side chains as the interior of a protein is hydrophobic and the exterior is hydrophilic
What type of proteins are ‘inside out’?
Membrane proteins typically have hydrophobic exteriors and hydrophilic interiors as they exist in the hydrophobic environment of the cell membrane
Why can folding not be random?
The folding can not be random as if each amino acid was to select each possible conformation in order to find the most stable this would take too long to fold
How does protein folding occur?
Protein folding occurs through several stages beginning with a rapid molten globule collapse where the hydrophobic chains are buried, this is followed by subsequent fine tuning which is a slow search of the protein for stable structures where the correct sections are retained but incorrect section are either altered by the protein itself or by molecular chaperones
What occurs in the energetics of free energy in protein folding?
There is a small net negative energy change for the process of protein folding, this is made up of an enthalpic energy release from the formation of the many weak bonds such as hydrogen bonds that make up protein structure which is slightly offset by an increase in entropy as the protein now has one conformation rather than several possible conformations
What are the effects of having proteins which are marginally stable?
Aids in making proteins flexible
Allows for cells to be able to denature and degrade proteins when appropriate
Proteins do often need help from molecular chaperones in order to fold correctly
Proteins can potentially misfold causing disease such as prion diseases
How can the cis and trans isomers of proline influence protein folding?
The isomerisation of prolines can be a rate-limiting step in proteins this can be reduced by peptidyl prolyl isomerases which increases the rate of isomerisation
How can disulphide bonds control the rate of protein folding?
There may be several possible ways in which disulphide bonds can be arranged, these will be trialled between disulphide bond isomerases until the correct arrangement is found
Do all proteins adopt a fixed conformation?
No, many proteins will only fold if they are in te correct biological context
What amino acids tend to favour an alpha helix?
Alanine, Cystine, Leucine, Methionine, Glutamate, Glutamine, Histidine and Lysine
What amino acids tend to favour a beta sheet?
Valine, Isoleucine, Phenylalainine, Tyrosine, Tryptophan, threonine
What amino acids tend to favour a turn in the random coil?
Glycine, Serine, Aspartate, Aspargine, Proline
