Engineering Proteins

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Engineering Proteins

• EP2 Protein Synthesis

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Amino Acids
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Some of the 20 Naturally Occurring Amino Acids
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Amino Acids - Summary

• Zwitterions
• Acid / Base Chemistry (Buffers)
• Optical Isomerism chiral centre, CORN
• Peptide Secondary Amides
• Naming dipeptides NH2 on left
• Hydrolysis of peptides
• Condensation to form polypeptides and proteins

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Dipeptides
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Condensation
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Protein Structure

• 4 levels of structure-
• Primary Structure Sequence of Amino Acids
• Secondary Structure Spatial arrangement of
  sections of primary Structure (e.g. helices)
• Tertiary Structure Overall 3D Shape of protein
• Quaternary Structure Protein Monomers
  coordinated into tetramers (haemoglobin), or
  hexamers (insulin).

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Primary Structure
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Secondary Structure
? - Helix
? - Sheet
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Tertiary Structure gyrase
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Quaternary Structure Insulin Hexamer
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Insulin Hexamer
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Building Proteins

• Cells build proteins directly from L-Amino Acids.
• To synthesise a protein, a Chemist would need-
• Instructions / knowledge of the primary
  structure
• Supplies of pure amino acids
• A method of forming peptide links.
• Cells adopt a similar approach Protein
  Synthesis.

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Protein synthesis The role of RNA

• Messenger RNA - Temporary set of instructions for
  one protein molecule
• 2) Transfer RNA collects amino acids
• 3) Ribosomal RNA present in ribosomes, which
  catalyse the formation of peptide links between
  amino acids.

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1) Messenger RNA (mRNA)
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2) Transfer RNA (tRNA)
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3) Ribosomal RNA (rRNA)
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What is RNA? ribonucleic acid
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Nucleic Acids
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mRNA triplet base codes (ppt)
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RNA Base Pairs
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A Permanent set of Instructions

• DNA

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DNA deoxyribonucleic acid

• Codes for many mRNA molecules.
• The section of DNA coding for a particular
  protein is called a gene.
• Full set of genes genome
• (humans 3.5 x 109 bases)

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Differences between RNA and DNA
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DNA Base Pairs
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DNA
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DNA
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How Cells Make Proteins
DNA
mRNA
Transcription
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Transcription
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Transcription in the nucleus

• 1) DNA double helix unwinds
• 2) hydrogen bonds break
• 3) free nucleotides hydrogen bond to the
  complementary exposed bases
• 4) Enzyme (RNA polymerase) links the hydrogen
  bonded nucleotides to form a strand of mRNA
• 5) mRNA is released and the DNA double helix is
  reformed.

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How Cells Make Proteins
Protein Chain
DNA
mRNA
Transcription
Translation
a.a. activation
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Amino Acid Activation
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Amino Acid Activation

• tRNA molecule forms an ester link with a specific
  amino acid
• tRNA amino acid complex moves to the Ribosome.

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Translation (ppt)
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Translation - in the cytoplasm

• mRNA attaches to ribosome
• Hydrogen bonding between complementary bases
  binds the correct tRNA anticodon to the 1st codon
  (set of 3 bases on mRNA)
• A 2nd tRNA amino acid complex binds to the
  adjacent mRNA codon in the ribosome
• Ribosome catalyses the formation of the peptide
  bond between amino acids
• The tRNA is released once the amino acid is
  delivered
• Ribosome moves along the mRNA chain to the end.

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How Cells Make Proteins
Protein Chain
3D Protein
DNA
mRNA
Transcription
Translation
Folding
a.a. activation
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Protein Synthesis
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How Cells Make Proteins
Protein Chain
3D Protein
DNA
mRNA
Transcription
Translation
Folding
a.a. activation