Chapter 3a - Protein function

Chapter 3a - Protein function - Chapter 3 PROTEIN FUNCTION...

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Chapter 3 PROTEIN FUNCTION
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All proteins bind to other molecules Binding is selective
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The protein’s conformation determines its chemistry
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cAMP-binding site in a protein
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Chemistry at an active site A “catalytic triad” in serine proteases. The side chain of Asp 102 induces His 57 to remove the proton from Ser 195. The activated serine in turn forms a covalent bond with the enzyme substrate, hydrolyzing a peptide bond
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Sequence comparisons between protein family members highlight crucial ligand binding sites “Evolutionary tracing” identifies sites in a protein domain that are most crucial to the domain’s function
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Proteins bind to other proteins through several types of interfaces
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Surface-string interaction allows the SH2 domain to recognize a phosphorylated polypeptide as a loop on a second protein
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Binding sites in proteins – each antibody recognizes a specific target
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Noncovalent bonds mediate interactions between macromolecules
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Greater the equilibrium constant, greater the binding strength. This is a direct measure of the free-energy difference between the bound and the free states
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Enzymes are powerful and highly specific catalysts
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K m is a measure of how tightly the substrate is bound. Substrate binding is the first step in enzyme catalysis
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Enzymes speed reactions by selectively stabilizing transition states or in other words by decreasing the activation energy The free energy required to attain the most unstable transition state is called the activation energy for the reaction, and it is the major determinant of the reaction rate
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One of the most important factors in enzyme catalysis is the ability of an enzyme to bind substrate more tightly in its transition state than in its ground state. The difference in binding energy between these states lowers the activation energy of the reaction. This is
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This note was uploaded on 09/22/2011 for the course BIO 320 taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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Chapter 3a - Protein function - Chapter 3 PROTEIN FUNCTION...

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