Engineering Proteins EP2 Protein Synthesis. Amino Acids.
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Transcript of Engineering Proteins EP2 Protein Synthesis. Amino Acids.
Engineering Proteins
EP2 Protein Synthesis
Amino Acids
Some of the 20 Naturally Occurring Amino Acids
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
Dipeptides
Condensation
Protein Structure
4 levels of structure:-oPrimary Structure – Sequence of Amino Acids;
oSecondary Structure – Spatial arrangement of sections of primary Structure (e.g. helices);
oTertiary Structure – Overall 3D Shape of protein;
oQuaternary Structure – Protein “Monomers” coordinated into tetramers (haemoglobin), or hexamers (insulin).
Primary Structure
Secondary Structure
- Helix - Sheet
Tertiary Structure – gyrase
Quaternary Structure – Insulin Hexamer
Insulin Hexamer
Building Proteins
Cells build proteins directly from L-Amino Acids.
To synthesise a protein, a Chemist would need:-
1) Instructions / knowledge of the primary structure;2) Supplies of pure amino acids;3) A method of forming peptide links.
Cells adopt a similar approach – Protein Synthesis.
Protein synthesis – The role of RNA
1) 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.
1) Messenger RNA (mRNA)
2) Transfer RNA (tRNA)
3) Ribosomal RNA (rRNA)
What is RNA? – ribonucleic acid
Nucleic Acids
mRNA triplet base codes (ppt)
RNA Base Pairs
A Permanent set of Instructions
DNA
DNA – deoxyribonucleic acid
1) Codes for many mRNA molecules.
2) The section of DNA coding for a particular protein is called a gene.
3) Full set of genes = genome (humans 3.5 x 109 bases)
Differences between RNA and DNA
DNA Base Pairs
DNA
DNA
How Cells Make Proteins
DNA mRNA
Transcription
Transcription
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.
How Cells Make Proteins
DNA mRNA
Protein
Chain
Transcription
Translation
a.a. activation
Amino Acid Activation
Amino Acid Activation
1. tRNA molecule forms an ester link with a specific amino acid;
2. tRNA – amino acid complex moves to the Ribosome.
Translation (ppt)
Translation - in the cytoplasm
1) mRNA attaches to ribosome;2) Hydrogen bonding between complementary bases
binds the correct tRNA anticodon to the 1st codon (set of 3 bases on mRNA);
3) A 2nd tRNA – amino acid complex binds to the adjacent mRNA codon in the ribosome;
4) Ribosome catalyses the formation of the peptide bond between amino acids;
5) The tRNA is released once the amino acid is delivered;
6) Ribosome moves along the mRNA chain to the end.
How Cells Make Proteins
DNA mRNA
Protein
Chain
3D Protei
n
Transcription
Translation
a.a. activation
Folding
Protein Synthesis
How Cells Make Proteins
DNA mRNA
Protein
Chain
3D Protei
n
Transcription
Translation
a.a. activation
Folding