LS3protein function

LS3protein function - Lecture 3: Function of proteins -most...

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1 Lecture 3: Function of proteins -most work in the cell are done by proteins, how do proteins work? 1. Protein family Why different proteins have different functions? 2. How do proteins work? -antibodies -enzymes 3. How are proteins regulated in the cell -Proteins with similar sequence often have the similar structure and similar function -Proteins with the similar structure/function are grouped together as protein families, members of the same protein family are usually evolutionarily related -Different types of proteins: antibodies, enzymes, transcription factors, structural proteins, Transport proteins ... 1. Protein family
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2 Members of a protein family have similar amino acid sequences Myoglobin hemolobin 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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3 2. How proteins work? -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. -The protein-ligand interaction can be transient, stable, or permanent, but they are all specific -Protein function can be measured by its interaction with a ligand: affinity refers to the binding strength (measured by Kd), specificity refers to substrate preference Animals produce antibodies or immunoglobulins (Ig) in response to foreign molecules, small or large. Antibodies are highly specific, they can distinguish proteins that differ by only a single amino acid. Antibody-inducing agents are called antigens. The region of an antigen recognized by an antibody is called epitope. Antibodies bind tightly to specific antigens with > 10-9 M affinity. Protein works by specifically binding to other molecules e.g. Antibodies
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4 Antibodies or Immunoglobulins 1. antibody has 4 subunits An antibody molecule contains 4 polypeptide chains, two heavy chains (H), and two light chains (L), The variable domains contains the complementarity-determining region (CDR), which interacts with the antigen, whereas the constant domains allow each antibody to have similar structures. Each polypeptide chain can be divided into two domains, a variable domain (VL and VH), different in different antibody, and a constant domain, same in different antibody. Pathogens
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LS3protein function - Lecture 3: Function of proteins -most...

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