10. Translation

Chapter 27 Lehninger 5th Edition

Translation

• mRNA gets translated by Ribosomes

Bacterial ribosomes

Eukaryotic ribosomes in ER

The Genetic Code

• 4 bases -> 20 amino acids?

• 42 = 16 43 = 64

• Code = – Triplet code

• 3 bases -> 1 amino acid

– Non-overlapping– Degenerate

The Genetic Code

CodonsCodon usage

Ribosomes

• Need to:– Bind to mRNA

– Recognise start of coding sequence

– Move along coding sequence • Read RNA, codon by codon

• Add amino acids to protein chain

• Need an “adaptor” molecule– tRNA – Transfer RNA

tRNA: Transfer RNA

20 tRNA synthetases

1965: Yeast tRNAala

Ribosomes: 2 subunits• large• small

• S: Svedberg units; centrifugation “size”

Chuck Kurland

SSU rRNA

Translation Initiation

•Bacteria: RBS or Shine Dalgarno sequence•Eukaryotes: ?