Lecture 26

Lecture 26 - Enzymes have pockets where things fit per...

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Unformatted text preview: Enzymes have pockets where things fit per fectly Unstr uctured par t of polypeptide Lecture 26 Protein Function Ligand-binding: Selectivity Ligand : Molecule to which a protein binds Often causes a change in the shape of a protein Two properties characterize ligand binding: Affinity Selectivity Both depend of the specificity of the ligand binding site Selectivity : Ability of a protein to bind one molecule in preference to other molecules Ex: Have an enzyme and different substrates, what is the preference for a particular substrate Affinity : How strong two molecules bind Affinity constant K d K d : The stronger the interaction between a protein and a ligand, the lower the K d Page | 1 Different am ino acids being mutated Might not fit properly and thus pushes selectivity Some proteins might be selective but affinity might be weak Other might have st rong affinity but not be selective DNA selectivity for different base pairs can bind very st rongly Molecular complementarity For high affinity and high specificity: Shape and chemical properties of the binding site must be complementary to that of the ligand Molecular Complementarity: Antibodies CDR : Complimentarity determining region Tip that recognizes the epitope Antigen : Molecule that will make the host animal respond and produce antibodies against this antigens Each antibody recognized not the whole antigen Recognizes a very particular epitope Epitope : Region of the antigen recognized by one specific antibody Located at the surface of the antigen Not necessarily a linear sequence In cases of unfolding, the antibody might Page | 2 not recognize the epitope Enzymes Enzymes are efficient and specific catalysts Enzymes : Proteins that catalyze chemical reactions Substrates : Ligands of enzymes Catalyst : Enzyme that increases the rate of...
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Lecture 26 - Enzymes have pockets where things fit per...

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