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Published byDiana Carr Modified over 8 years ago
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3.12-3.13 Proteins – Pt. 2: Protein Folding Pg. 43-45 Objective: I can describe and explain how the folding of a protein determines its ability to function and errors in this can result in various diseases/disorders.
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Primary Structure = sequence of amino acids (20 types can be linked in any order) Secondary Structure = bends/twists in chain Caused by (mostly) hydrogen bonds 2 types = α-helix & β-sheets Tertiary Structure = overall shape of 1 polypeptide chain (from all bends/twists) Caused by cross-linking, “hydrophobic hiding” Quaternary Structure = overall structure of several polypeptide chains functioning protein Primary Structure Determines All Other Levels
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Enzymes (folded, functioning protein) have an active site: 3-D space/groove (shape) ▪Where molecules attach to be catalyzed
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What determines shape of protein? Location of folds – where folds occur ▪What determines where folds occur? ▪Sequence of A.A. (primary structure) Why? How?
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Proteins fold because… (review) Polar A.A. attract (H-bonds may form) Nonpolar A.A. repel watery environment Cross-linking from “special” A.A. (Sulfur) Folded proteins can perform function Has 3-D shape shape provides function ▪If unfolded…
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Proteins unfold because… Increase temperature: heat moves break Change pH: H + /OH - wants more than δ + /δ - (polarity) Both affect/break H-bonds How?
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Proteins (enzymes) can fold in MANY ways But need to have right shape to do function! Chaperonins can help new proteins fold correctly by isolating from environment
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Chaperone Proteins a.k.a. chaperonins Some chaperonins are heat-shock proteins Will help protein refold after high temperature denature Not always possible to “renature” back into right shape…
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Know sequence of MANY proteins= Do not know the conformation (structure/shape) When protein folded incorrectly, may lead to many diseases (often due to incorrect sequence primary ) : Sickle-cell anemia, Cystic fibrosis, Alzheimer’s, Huntington’s, Parkinson’s, and several cancers Prions – group of diseases where misfolded protein causes good, normal protein to misfold & malfunction Mad Cow’s Disease, Kuru (most affect the brain) Primary structure Secondary, Tertiary, Quaternary structure
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Because many diseases caused by proteins folded incorrectly, if can figure out correct way to fold, maybe can cure disesase Programs to figure out how proteins fold http://folding.stanford.edu/ http://folding.stanford.edu/ http://fold.it/portal/ http://fold.it/portal/
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If denatures (unfolds) = bad No shape, no function (heat, pH change) Usually, death If fold the wrong way = bad Does not perform proper function May misfunction disease If fold wrong way AND cause other good proteins to misfold = bad Prions = special disease
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