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Unformatted text preview: Lecture 4 Protein Structure Cont Quaternary structures consist of more than one protein/ more than one polypeptide. These proteins are called subunits They interact with the same forces as tertiary structures Protein modifications expand the function of whatever they are attached to o Lipoproteins bind to lipids o Metalloproteins bind to metal ions o Hemoproteins have an attached heme group Protein folding pathways are specified by their sequence. Protein structures are held together purely by weak interactions - hydrogen bonds, electrostatic interactions, van der Waal's packing and hydrophobic interactions. A single weak interaction contributes very little to the stability of a protein structure, yet the very large number of these interactions act together co-operatively to impart high stability to the protein fold. Co-operativity in a folding process demonstrates that the stability of the folded state is greater than the sum of the...
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