27_Lieb_Translation - Lieb Biology 202 Translation Protein...

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Lieb- Biology 202 Translation & Protein Structure Page 1 of 4 I. Polypeptides Amino acids have a central (alpha) carbon atom attached to an amino group (NH 2 ) a carboxyl group (COOH) a side chain (R, for reactive group). In a polypeptide, amino acids are linked by peptide bonds between the carboxyl group of one aa and the amino group of the next. Because this is a dehydration reaction (water is removed), we often refer to amino acid residues in a polypeptide. Just as nucleic acid strands have polarity (a 5' end and 3' end), so do polypeptides. They have an amino terminus and carboxy terminus . II. Levels of protein structure primary structure : sequence of amino acids in a polypeptide. Similarity in amino acid sequence can be used to find evolutionary relationships among proteins and to define families or conserved proteins. motifs or blocks are short regions of conserved sequence (and usually conserved function) that can often be recognized in the primary structure. secondary structure : small structures formed by neighboring amino acid residues. Secondary structures are the basic units that give proteins their shape. alpha helix : a helix stabilized by hydrogen bonds beta pleated sheet : anti-parallel strands stabilized by hydrogen bonds secondary structures can often be predicted from the primary structure tertiary structure : complex folding of entire polypeptide chain into 3D structure. A domain is a region of a polypeptide that folds into a particular structure. quaternary structure : some proteins contain more than one polypeptide (multimers). For example, myosin is a homodimer (two identical monomers make the protein)
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This note was uploaded on 03/02/2009 for the course BIOL 201 taught by Professor Mitchell during the Spring '07 term at UNC.

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27_Lieb_Translation - Lieb Biology 202 Translation Protein...

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