Lecture3

Lecture3 - How proteins work-Proteins work by binding to...

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How proteins work? -A protein’s structure determines its function -Proteins with the similar function can be grouped together called protein families, members of the same protein family usually have similar structures structural proteins, enzymes, transcription factors signal transduction proteins -Proteins work by binding to other molecules, called ligands or substrates, including small ones such as ions or sugars, and large ones such as proteins, DNA, and RNA.
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Homology between the amino acid sequences of myoglobin and α− globin Myoglobin α -globin
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Members of a protein family have similar structure and function 16 kD Single peptide protein Muscle O 2 carrier 64 kD 4-subunit protein blood O 2 carrier
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Enzyme Enzyme ± The suffix “-ase” is usually appended to the name: ± Protease (degrade protein) ± Kinase (add Pi) ± Phosphatase (remove Pi) ± Ribonuclease (RNase:degrade RNA) ± etc.
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Enzymes are proteins that catalyze reactions Enzymes are proteins that catalyze reactions Substrates Substrates Products Products Enzyme Enzyme ± enzyme converts a substrate to a product without changing itself ± Enzymes speed up reactions by factors of 10 6 or more at relatively low temperature ± Enzymes are highly specific and function by lowering the activation energy of the reaction
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Δ G Enzymes lower the activation energy
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How is the enzymatic activity measured? V max –maximum rate of the reaction the bigger the V max, the more active the enzyme K m –substrate concentration at 1/2 V max . the smaller the K m , the higher the enzyme- substrate affinity (or the “better” the enzyme)
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Antibodies or Antibodies or Immunoglobulins Immunoglobulins
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Pathogens Bloodstream Bloodstream Bacteria Viruses Fungi infection Approximately 1 million B cells, each with a different antibody on the cell surface. A small fraction will be capable of binding pathogen (through appropriate non-covalent bonds). Antibodies secreted into bloodstream bind and neutralize pathogens. expansion A A C C D D E E F B F B Pathogen A A F F E E F F F F F F F F F F and secretion F F F F F F F F
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Antibodies as Molecular Tools ± Animals produce antibodies in response to the injection of foreign materials(Antigens). ± Antibodies bind tightly to specific antigens with > 10 -9 M affinity. ± Antibodies can distinguish among proteins that differ by only a single amino acid. ± Antibodies can be used to determine if a particular protein is present in a complex mixture of proteins. ± Antibodies can also be used to purify a
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Lecture3 - How proteins work-Proteins work by binding to...

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