1. Biosynthesis and degradation of proteins
Bruno Sopko

2. Content Proteosynthesis Post-translation processing of proteins
Protein degradation

3. Proteosynthesis Aminoacyl-tRNA formation Iniciation Elongation
Termination

4. Aminoacyl-tRNA formation
Amino acid + ATP ↔ Aminoacyl-AMP + PPi
Aminoacyl-AMP + tRNA ↔ Aminoacyl-tRNA + AMP
Each amino acid has „its own“ tRNA and aminoacyl-tRNA synthetase (ARS)
Reactions are cytosolic
Errors are corrected by specific correcting enzymes
ARS have other enzyme activity (other signaling molecule?)

5. Other ARS functions

6. Proteosynthesis Iniciation

7. Elongation

8. Termination

9. Post-translation processing of proteins
Secondary structure and role of the chaperons
Proteolytic modifications
Glycosylation
Other modifications (hydroxylation, phosphorylation, acetylation, methylation, carboxylation)

10. Protein transfer after translation

11. Contranslational translocation

12. Contranslational translocation –transmembrane proteins

13. Transmembrane proteins - examples
Type I – glycophorin, LDL receptor, influenza HA protein, insulin receptor, growth hormone receptor …
Type II – transferrin receptor, influenza HN protein, Golgi sialyltransferase, Golgi galactosyltranferase …
Type III – cytochrome P450 …
Type IV – G-protein, glucose receptors (GLUT 1 …), connexin, voltage gated Ca2+ channel …

14. Secondary structure

15. Secondary structure –HSP70 chaperon cycle

16. Secondary structure – GroEL/GroES system

17. Secondary structure – overview

18. Protein disulfid isomerase (PDI) and peptidyl prolyl cis-izomerase
PPI:

19. Proteolytic modification - insulin

20. N-Glycosylation

21. Other modifications O-glycosylation
Hydroxylation (hydroxyproline, hydroxylysine)
Methylation (mono- , di- and even trimethyllysine)
PHOSPHORYLATION
Carboxylation (γ-carboxyglutamate, vitamin K, fibrinogen)
Acetylation
……..

22. Protein degradation Proteases Protein degradation systems
Ubiquitin and proteasome
Activation of proteases
Protease inhibitors

23. Proteases Serine proteases (trypsin, chymotrypsin, elastase ….)
Aspartate proteases (pepsin, some proteases found in lysosomes, renin, HIV-protease …)
Metalloproteases (carboxypeptidases, various matrix metalloproteases …)
Cysteine proteases (papain, cathepsins, caspases, calpains …)

24. Protein degradation systems
Vacuolar (lysosomes, endosomes, ER, …)
Ubiquitin pathway (proteasome)

25. Ubiquitin pathway

26. Activation of proteases
Most proteases are synthesized as larger pre-proteins. During activation, the pre-protein is cleaved to remove an inhibitory segment.
In some cases activation involves dissociation of an inhibitory protein
Activation may occur after a protease is delivered to a particular compartment within a cell or to the extracellular milieu.
Caspases involved in initiation of apoptosis are activated by interaction with large complexes of scaffolding and activating proteins called apoptosomes.

27. Protease inhibitors
IAPs are proteins that block apoptosis by binding to and inhibiting caspases. The apoptosis-stimulating protein Smac antagonizes the effect of IAPs on caspases.
TIMPs are inhibitors of metalloproteases that are secreted by cells. A domain of the inhibitor protein interacts with the catalytic Zn2+. 
Cystatins are inhibitors of lysosomal cathepsins. Some of these (also called stefins) are found in the cytosol and others in the extracellular space. Cystatins protect cells against cathepsins that may escape from lysosomes.
Serpins are widely distributed proteins that utilize a unique suicide mechanism to inhibit serine or cysteine proteases. A large conformational change in the serpin accompanies cleavage of its substrate loop. This leads to disordering of the protease active site, preventing completion of the reaction. The serpin remains covalently linked to the protease as an acyl-enzyme intermediate.
Non-specific: α2-macroglobulin

28. Fate of the protein

29. Literature
Marks´ Basic Medical Biochemistry, A Clinical Approach, third edition, 2009 (M. Lieberman, A.D. Marks)
B. Wilkinson, H.F. Gilbert / Biochimica et Biophysica Acta 1699 (2004) 35–44
F. Ulrich Hartl, Andreas Bracher & Manajit Hayer-Hartl, Molecular chaperones in protein folding and proteostasis, Nature 475 (2011)