Amino Acids and the Primary Structures of Proteins

1. Amino Acids and the PrimaryStructures of Proteins

2. Firefly Luciferase and Luciferin

3. Hemoglobin in erythrocytes

4. Keratin

5. Chemical structure ofan amino acid R = side chain Carboxyl terminus C = alpha carbon Amino terminus R = side chain

6. The alphacarbon of amino acids is chiral (except glycine). There are two stereoisomers of amino acids (L and D). Proteins contain L-amino acids

7. L-amino acidat neutral pH Figure 3.1

8. Amino acids with aliphatic R groups

9. The amino acid proline is a cyclic molecule

10. Amino acids with aromatic R groups

11. Amino acids with sulfur-containing R groups

12. Oxidation can form cystine from two cysteines Figure 3.4

13. Side chains with alcohol groups

14. Amino acids with basic R groups

15. Amino acids with acidic R groups

16. Amide derivatives of acidic R groups

17. Other amino acids and amino acid derivatives Figure 3.5

18. Selenocysteine is the 21st amino acid

19. Ionization of amino acids Pages 63 – 67 pH ? pH ?

20. Ionization of amino acids Pages 63 – 67 pH 1 pH 7

21. Ionization of amino acids Pages 63 – 67 pH ? pH 7

22. Ionization of amino acids Pages 63 – 67 pH 12 pH 7

24. Ionization of histidine Figure 3.7

25. Ionization of histidine Figure 3.7

27. Ionization of glutamate Figure 3.8

28. Ionization of arginine Figure 3.8

29. Peptide bonds link amino acids in proteins Figure 3.9

30. Peptide bonds link amino acids in proteins Figure 3.9 Alanine Ala (A) Serine Ser (S) DipeptideAla – Ser or AS

31. Practice Problem Draw the chemical structure of the tripeptide Ala – Thr– Cys at pH 7. Answer the following with regard to this tripeptide: 1. Indicate the charge present on any ionizable group(s). 2. Indicate, using an arrow, which covalent bond is the peptide bond. 3. What is the net, overall charge of this tripeptide at pH 7? __________ 4. What is this peptide called using the one-letter code system for amino acids? ______

32. Proteins can be very large, hundreds of amino acids long The enzyme HMG-CoA reductase MLSRLFRMHGLFVASHPWEVIVGTVTLTICMMSMNMFTGNNKICGWNYECPKFEEDVLSSDIIILTITRCIAILYIYFQFQNLRQLGSKYILGIAGLFTIFSSFVFSTVVIHFLDKELTGLNEALPFFLLLIDLSRASTLAKFALSSNSQDEVRENIARGMAILGPTFTLDALVECLVIGVGTMSGVRQLEIMCCFGCMSVLANYFVFMTFFPACVSLVLELSRESREGRPIWQLSHFARVLEEEENKPNPVTQRVKMIMSLGLVLVHAHSRWIADPSPQNSTADTSKVSLGLDENVSKRIEPSVSLWQFYLSKMISMDIEQVITLSLALLLAVKYIFFEQTETESTLSLKNPITSPVVTQKKVPDNCCRREPMLVRNNQKCDSVEEETGINRERKVEVIKPLVAETDTPNRATFVVGNSSLLDTSSVLVTQEPEIELPREPRPNEECLQILGNAEKGAKFLSDAEIIQLVNAKHIPAYKLETLMETHERGVSIRRQLLSKKLSEPSSLQYLPYRDYNYSLVMGACCENVIGYMPIPVGVAGPLCLDEKEFQVPMATTEGCLVASTNRGCRAIGLGGGASSRVLADGMTRGPVVRLPRACDSAEVKAWLETSEGFAVIKEAFDSTSRFARLQKLHTSIAGRNLYIRFQSRSGDAMGMNMISKGTEKALSKLHEYFPEMQILAVSGNYCTDKKPAAINWIEGRGKSVVCEAVIPAKVVREVLKTTTEAMIEVNINKNLVGSAMAGSIGGYNAHAANIVTAIYIACGQDAAQNVGSSNCITLMEASGPTNEDLYISCTMPSIEIGTVGGGTNLLPQQACLQMLGVQGACKDNPGENARQLARIVCGTVMAGELSLMAALAAGHLVKSHMIHNRSKINLQDLQGACTKKTA

33. Next:Chapter 4Proteins: Three-DimensionalStructure and Function