oct 16 - Proteins T h e s t r u c t u r e o f in s u lin ....

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1 Proteins A protein is a gene product. Proteins are the effectors of cell function--enzymes; molecular motors; signaling molecules; membrane channels. Proteins also play structural roles. Proteins are very diverse. The genome of any given animal species contains 10 4 different protein-coding genes. •The structure of insulin. •Left is space-filling model of the biologically active form. •Right is a ribbon diagram of the stored form. 5’ Amino end of chain 3’ Carboxy end of chain A protein is a gene product. The central or “ α ” carbon is covalently bound to: 1) a hydrogen atom; 2) an amino group (NH 3 + ); 3) a carboxyl group (COO - ); 4) a variable sidechain called an R Group . It is the chemical structure of this sidechain that distinguishes the 20 amino acids used by cells. ! urve " # ig. 3.5 CHEMICAL STRUCTURE OF AN AMINO ACID α carbon The sequence of amino acids within a polypeptide is a direct readout of the codons (= nucleotide sequence) of its mRNA. Right: amino acid sequence of the anti- bacterial enzyme lysozyme. Peptide bond This is uncharged form of the basic structure, common to all amino acids. • Look at the R groups (side-chains) • What’s important? -recognize their properties -predict what kind of bonds an R group could form with another
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2 The primary structure of a polypeptide is the linear array of its amino acids. The amino acids within the polypeptide chain are connected by covalent peptide bonds. Peptide bonds ! urve " # ig. 3.4 PEPTIDE BOND PEPTIDE BOND During translation, the ribosome causes a covalent bond to form between the carbon atom of a carboxyl group and the nitrogen
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oct 16 - Proteins T h e s t r u c t u r e o f in s u lin ....

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