Chapter 3 - Chapter 3 1.22.08 Ig structure/Ag-Ab...

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Chapter 3 1.22.08 Ig structure/Ag-Ab interactions - Classic pathway – complement activated by antibodies QUIZ on Thursday over antibody worksheet Immunoglobin domains – blue swirlies - Two main functions: bind pathogens/antigen and recruit other components of the immune system - Three globular regions for a Y shape. 2 antigen binding sites are at the tip of the arms, tethered by a flexible hinge region - V = variable region for light chains, at N terminus - C = conserved region for light chain, at C terminus - Heavy chain has 3 conserved and 1 variable - All connected by disulfide bonds Antibody diagram - Heavy chains connected by disulfide hinges, light chains on the top. Light chains 25 kDa, heavy are 50 kDa, for a total of ~150 kDa o Each heavy chain linked to a light chain, and linked together - Subtypes: IgM, IgG (most abundant), IgD, IgA, IgE Proteolytic cleavage by papain – cleaves into 3 pieces, 2 Fab fragments and one Fc fragment - Fab – fragment that is antigen binding, contain V region - Fc is crystallizable, contains C regions Pepsin - Cleave disulfide bonds, producing F(ab’)2 Scanning EM of gold-coated antibodies - Antigen is a hapten (doesn’t provoke an immune response alone, small, bound to a carrier). Consists of 2 hapten molecules that can crosslink. o Linear, triangular, square. Pepsin digestion can remove spikes - Antigen is flexible Ig Domains – 110 amino acid, formed of 2 beta-pleated sheets oriented in an antiparallel orientation - Variable domain is a little bit larger. Loops confer specificity - Barrel shaped structured domains with B-strands running antiparallel to for 2 B-sheets held together by a disulfide bond. o C’ and C’’ in variable domains, not in C o 4 strand + 3 strand, or 4 strand + 5 strand typical Ab structure summary - 2 identical heavy chains (M, gamma, delta, alpha, epsilon) - 2 identical light chains ( kappa or lambda) - V region bind antigen, variable - C region constant - V and C regions Ig domains. 110 AA, 2 antiparallel beta pleated sheets sometimes called a beta-barrel Variability - Very little variability in most of the molecule (framework region)
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This note was uploaded on 04/17/2008 for the course BIO 4750 taught by Professor Leavey during the Spring '08 term at Georgia Institute of Technology.

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Chapter 3 - Chapter 3 1.22.08 Ig structure/Ag-Ab...

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