Flashcards in B2.023 Mutations that Alter Proteins: A Variety of Outcomes Deck (15):
what kinds of protein parameters can mutations alter?
folding/stability, concentration, location, post-translational modification, function
what factors affect alteration of protein concentration?
gene expression and protein degradation
what measure is affected by protein concentration?
vmax of catalysis or transport
what example was discussed with reference to post translational modifications of proteins?
cleaving of trypsinogen by enteropeptidase in small intestine to activate it into trypsin
trypsin then catalyzes activation of other enzymes
how do proteins bind to ligands?
specific amino acid interactionds, side chain or backbone
how can mutations alter binding?
affinity (how tightly it binds)
specificity (which lingand is bound most tightly)
how do we quantify binding affinities?
association reaction and dissociation reaction constants Ka and Kd
why is Kd particularly useful?
Kd=[L] when [P] = [PL] so you can tell how much ligand needs to be present to bind 50% of the protein (units M)
how do you plot ligand/protein binding?
[ligand] vs fraction bound
can be linear (hyperbolic shape) or log (sigmoidal shape)
how can a mutation in amino acid physically decrease binding stability in vitamin D resistant rickets?
if a smaller amino acid is subbed, lacks stabilizing interaction
how can a mutation in an ion channel protein affect the heart?
long QT syndrome can result from Na+ channels not opening/closing properly
how does HIV resist drugs?
mutations in the HIV protease can inhibit the drugs ability to bind to the active site, making the drug ineffective against that from of HIV
how do we get around drug resistance in HIV protease?
treat HIV with a cocktail of 8 drugs
what is protein moonlighting?
proteins can have more than one function