Lect_18_NAII

Lect_18_NAII - Peptide, Protein & Nucleic Acid...

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Small peptide synthesis : Glutathione Energy requirement per peptide bond made Large protein synthesis Amino acid activation t-RNAs aminoacyl-tRNA synthetase Translation inititiation elongation termination Energy requirement per peptide bond made Inhibitors of protein synthesis Posttranslational modification of proteins Phosphodiester bond formation - energy need Please fill out two evaluation sheets: for Instructor and for T.A. Instructor: Roy H. Doi T.A.: Mollie Wegner BIS 103, Section 1 Fall 2007 Turn in to the aisle after you have filled out the forms.
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Review Session Wednesday, December 12, 2007 198 Young Hall 6:00 - 8:00 p.m.
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Final exam Friday, December 14, 2007 2205 Haring Hall 6:00 - 8:00 pm Bring UCD 2000 blue Scantron sheet #2 lead pencil calculator
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The final exam will consist of 50 multiple choice questions worth 4 points each for a total of 200 points. The final exam will cover primarily the materials presented in lectures 13-18. General knowledge of the materials in lectures 1-12 will be expected. Please pass evaluation sheets to the aisle so that they can be picked up. Thank you.
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We have been discussing this quarter how the cell obtains energy and how the cell uses the energy to carry out chemical work. Most energy is used to synthesize proteins and nucleic acids. The cell has devised two ways to make peptides and proteins. When small peptides are made, less energy is required. When large proteins are made, much more energy is required.
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Synthesis of simple short peptides (MW about 1,000-2,000) by enzymes versus ribosome-dependent synthesis of large proteins (MW >5,000). This involves the synthesis of peptide bonds.
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BIS 103 - 18 - amide and peptide bond R-C-NH 2 = O Amide (an unsubstituted amide) R-C-NH-R O Peptide Bond (an N-substituted amide)
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Glutamine synthetase (GS): COOH l CH 2 CH 2 l l H 2 N-C-H l COOH C-O-P l CH 2 CH 2 l l H 2 N-C-H l COOH C-NH 2 l CH 2 CH 2 l l H 2 N-C-H l COOH O O ATP ADP Mg 2+ Glutamine synthetase GS + NH 3 + Pi + Glutamic acid Glutamine Acyl-phosphate Glu + NH 3 + ATP Gln + ADP + Pi (GS) GS GS One enzyme, one ATP, one amide bond An example of amide bond synthesis
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Glutamine is made by one enzyme in a two step reaction. In the first step there is activation of the carboxyl group with the formation of an acyl phosphate group and the formation of a γ -glutamyl acyl phosphate-enzyme complex. Then NH 3 , a good nucleophile displaces the acyl-P group to form glutamine, an amide, and inorganic P. The reaction requires one enzyme, glutamine synthetase and one ATP, and there is synthesis of one amide bond. The energy requirement is 1 ATP/amide bond formed.
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Synthesis of glutathione - a tripeptide that contains Glu, Cys,Gly glutamic acid cysteine glycine Note: two peptide bonds glutathione COOH I CH 2 I CH 2 I CH-NH 2 I COOH COOH I NH 2 -CH I CH 2 -SH COOH I CH 2 -NH 2 C I CH 2 I CH 2 I CH-NH 2 I COOH II O C I N CH I CH 2 -SH H II O COOH I N CH 2 H
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Lect_18_NAII - Peptide, Protein & Nucleic Acid...

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