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section3 - MIT Department of Biology 7.014 Introductory...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2005 Recitation Section 3 February 9-10, 2005 Biochemistry—Proteins A. CBS proteins, 3D representation The protein we will consider today and periodically throughout the term is the yeast cystathionine beta synthase (CBS) protein. Today we will see gels visualizing wild-type and mutants versions of the yeast CBS protein. Yeast that lack CBS protein can not synthesize the amino acid cysteine. Mutant versions of the human CBS protein can lead to a very serious disease called homocystinuria. Some symptoms include mental retardation, early strokes and heart disease. First consider a crystallographic model of a form of CBS protein. Open the CBS structure html file in Internet Explorer. Rotate the molecule and get an idea of the three dimensional structure of CBS. The true 3-dimensional structure of CBS can be observed using the “Show Spacefill” button, and a trace of the peptide backbone can be observed using the “Show Ribbon” button. 1. What is the primary structure of a protein? What information does the modeling program provide us about the primary structure of CBS? 2. What is the secondary structure of a protein? What information does the modeling program provide us about the secondary structure of CBS? 3. What is the tertiary structure of a protein? What information does the modeling program provide us about the tertiary structure of CBS? 4. What is the quaternary structure of a protein? What information does the modeling program provide us about the quaternary structure of CBS? (Hint: Use the “Color Ribbon by Protein Subunit” button)
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B. Protein gels 1. Yeast cells produce enough CBS to fulfill their needs depending on the conditions in which they are growing.
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This note was uploaded on 01/19/2012 for the course BIOL 7.014 taught by Professor Walker during the Spring '05 term at MIT.

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section3 - MIT Department of Biology 7.014 Introductory...

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