Lecture 8

Lecture 8 - Lecture 8 2/2/10 Background reading: Garrett...

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Lecture 8 2/2/10 Background reading: Garrett and Grisham: Chapter 5: Pages 132-143 Outline: ± Protein domains ± Immunoglobulin G ± Origin of protein diversity Intragenic mutation Gene duplication Segment shuffling ± Fibrous proteins Collagen Proteins with coiled-coil framework ± Post-translational modifications
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Have considered the four levels of protein structure. As work progressed on many proteins, it became evident that another unit of organization exists that is distinct from these four levels. ± Protein domains A protein domain is a substructure produced by any part of a peptide chain that can fold independently into a compact, stable structure. Usually can contain regions as small as 40 amino acids but can be as big as over 300 amino acids. Different functions are often associated with these domains. The immunoglobulin molecule is a good example of a protein that contains domains. These proteins are antibodies and play a major role in the immune system which functions in defense.
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± Immunoglobulin G A heterotetramer composed of two types of chains: H = Heavy chain L = Light chain Each H chain contains 4 domains Each L chain contains 2 domains Each domain is a compact unit stabilized by a disulfide linkage.
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L chain Limited treatment of the molecule with a protease can separate the domains from one another.
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± Origin of protein diversity Analysis of human genome shows about 25,000 genes as compared to prokaryotic cells which have about 1,000 – 5,000 genes. Most of our genes probably arose during evolution from preexisting genes.
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Lecture 8 - Lecture 8 2/2/10 Background reading: Garrett...

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