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Amino Acids and the Primary Structures of Proteins. Firefly Luciferase and Luciferin. Hemoglobin in erythrocytes. Keratin. Chemical structure of an amino acid R = side chain. Carboxyl terminus. C = alpha carbon. Amino terminus. R = side chain.
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Amino Acids and the PrimaryStructures of Proteins
Chemical structure ofan amino acid R = side chain Carboxyl terminus C = alpha carbon Amino terminus R = side chain
The alphacarbon of amino acids is chiral (except glycine). There are two stereoisomers of amino acids (L and D). Proteins contain L-amino acids
L-amino acidat neutral pH Figure 3.1
Other amino acids and amino acid derivatives Figure 3.5
Ionization of amino acids Pages 60 – 64 pH ? pH ?
Ionization of amino acids Pages 60 – 64 pH 1 pH 7
Ionization of amino acids Pages 60 – 64 pH ? pH 7
Ionization of amino acids Pages 60 – 64 pH 12 pH 7
Ionization of histidine Figure 3.7
Ionization of histidine Figure 3.7
Ionization of glutamate Figure 3.8
Ionization of arginine Figure 3.8
Peptide bonds link amino acids in proteins Figure 3.9
Peptide bonds link amino acids in proteins Figure 3.9 Alanine Ala (A) Serine Ser (S) DipeptideAla – Ser or AS
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? ______
Proteins can be very large, hundreds of amino acids long The enzyme HMG-CoA reductase MLSRLFRMHGLFVASHPWEVIVGTVTLTICMMSMNMFTGNNKICGWNYECPKFEEDVLSSDIIILTITRCIAILYIYFQFQNLRQLGSKYILGIAGLFTIFSSFVFSTVVIHFLDKELTGLNEALPFFLLLIDLSRASTLAKFALSSNSQDEVRENIARGMAILGPTFTLDALVECLVIGVGTMSGVRQLEIMCCFGCMSVLANYFVFMTFFPACVSLVLELSRESREGRPIWQLSHFARVLEEEENKPNPVTQRVKMIMSLGLVLVHAHSRWIADPSPQNSTADTSKVSLGLDENVSKRIEPSVSLWQFYLSKMISMDIEQVITLSLALLLAVKYIFFEQTETESTLSLKNPITSPVVTQKKVPDNCCRREPMLVRNNQKCDSVEEETGINRERKVEVIKPLVAETDTPNRATFVVGNSSLLDTSSVLVTQEPEIELPREPRPNEECLQILGNAEKGAKFLSDAEIIQLVNAKHIPAYKLETLMETHERGVSIRRQLLSKKLSEPSSLQYLPYRDYNYSLVMGACCENVIGYMPIPVGVAGPLCLDEKEFQVPMATTEGCLVASTNRGCRAIGLGGGASSRVLADGMTRGPVVRLPRACDSAEVKAWLETSEGFAVIKEAFDSTSRFARLQKLHTSIAGRNLYIRFQSRSGDAMGMNMISKGTEKALSKLHEYFPEMQILAVSGNYCTDKKPAAINWIEGRGKSVVCEAVIPAKVVREVLKTTTEAMIEVNINKNLVGSAMAGSIGGYNAHAANIVTAIYIACGQDAAQNVGSSNCITLMEASGPTNEDLYISCTMPSIEIGTVGGGTNLLPQQACLQMLGVQGACKDNPGENARQLARIVCGTVMAGELSLMAALAAGHLVKSHMIHNRSKINLQDLQGACTKKTA
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