Protein synthesis

Unusual bases in tRNA

“Wobble” hypothesis

Functional domains of a ribosome

Charging of tRNA/Aminoacylation

Translation - 4 main steps

1. Charging of tRNA

2. Initiation

3. Elongation (3 steps)

4. Termination

Initiation in Prokaryotes

Elongation in Prokaryotes

Elongation in Prokaryotes

Termination in Prokaryotes

Proofreading on the ribosomeThe GTPase activity of EF-Tu .

Polyribosomes (or polysomes)

Initiation of translation in eukaryotesFirst step

2nd step

3rd step

POST TRANSLATIONAL CHANGESDealing with N terminal residue

Modification of individual amino acidsAcetylationPhosphorylation

Proteins have variable life-spans

EnzymeHalf-life Hours

Ornithine decarboxylase 0.2

RNA polymerase I 1.3

Tyrosine aminotransferase 2.0

Serine dehydratase 4.0

PEPcarboxylase 5.0

Aldolase 118

GAPDH 130

cytochrome c 150

Life-span factors

• Natural stability ("genetically encoded")– an inherent biophysical characteristic

• Change in environment– temperature– pH

• Active degradation– specific mechanism – location– partners

Terminology• Half-life -• Turnover -• Stability -• Denaturation -• Degradation -

Ubiquitin mediates degradation for many but not all proteins

Sticky ends