B2.023 Mutations that Alter Proteins: A Variety of Outcomes Flashcards

1
Q

what kinds of protein parameters can mutations alter?

A

folding/stability, concentration, location, post-translational modification, function

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2
Q

what factors affect alteration of protein concentration?

A

gene expression and protein degradation

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3
Q

what measure is affected by protein concentration?

A

vmax of catalysis or transport

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4
Q

what example was discussed with reference to post translational modifications of proteins?

A

cleaving of trypsinogen by enteropeptidase in small intestine to activate it into trypsin

trypsin then catalyzes activation of other enzymes

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5
Q

how do proteins bind to ligands?

A

specific amino acid interactionds, side chain or backbone

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6
Q

how can mutations alter binding?

A

affinity (how tightly it binds)

specificity (which lingand is bound most tightly)

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7
Q

how do we quantify binding affinities?

A

association reaction and dissociation reaction constants Ka and Kd

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8
Q

why is Kd particularly useful?

A

Kd=[L] when [P] = [PL] so you can tell how much ligand needs to be present to bind 50% of the protein (units M)

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9
Q

how do you plot ligand/protein binding?

A

[ligand] vs fraction bound

can be linear (hyperbolic shape) or log (sigmoidal shape)

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10
Q

how can a mutation in amino acid physically decrease binding stability in vitamin D resistant rickets?

A

if a smaller amino acid is subbed, lacks stabilizing interaction

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11
Q

how can a mutation in an ion channel protein affect the heart?

A

long QT syndrome can result from Na+ channels not opening/closing properly

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12
Q

how does HIV resist drugs?

A

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

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13
Q

how do we get around drug resistance in HIV protease?

A

treat HIV with a cocktail of 8 drugs

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14
Q

what is protein moonlighting?

A

proteins can have more than one function

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15
Q

what are 4 complicating factors in the study of protein function?

A
  1. moonlighting
  2. normal polymorphisms can interact differently with the environment
  3. environment includes other proteins
    - partners can have exacerbating or compensatory mutations
  4. current computer algorithms predict good/bad for missense mutations, but risk could be intermediate
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