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:- 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).

Primary Structure

Secondary Structure  - Helix  - Sheet

Tertiary Structure – gyrase

Quaternary Structure – Insulin Hexamer

Insulin Hexamer

Building Proteins Cells adopt a similar approach – Protein Synthesis. 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.

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.

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 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)

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 Protein Chain DNA mRNA Transcription Translation a.a. activation

Amino Acid Activation

Amino Acid Activation tRNA molecule forms an ester link with a specific amino acid; tRNA – amino acid complex moves to the Ribosome.

Translation (ppt)

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.

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

Protein Synthesis

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