Gram positive

1. Lecture 5: Protein translocation Gram negative Gram positive

2. Why do bacteria need to secrete or translocate proteins? bacteria move: they have flagella bacteria secrete proteins into their host during pathogenesis: type III or IV secretion systems

3. Why do bacteria need to secrete or translocate proteins? Bacteria secrete toxins: Examples: Cholera toxin: enzyme that activates host adenylate cyclase Botulinum toxin: causes flaccid paralysis» Cleaves synaptobrevin to inhibit release of acetylcholine in peripheral nerves E. coli haemolysin: Induce cytolytic effects by insertion into the target cell membrane Adhesins: proteins located on the outer membrane to facilitate interaction between the bacteria and their hosts example: Yersinia YadA

4. Why do bacteria need to secrete or translocate proteins? Bacteria need autolysins and PBPs at the periplasm: you should now what for already ;-) Bacteria translocate proteins involved in LPS biosynthesis: flippases, polymerase Bacteria may secrete or translocate proteins that mediate antibiotic resistance: example beta-lactamase Bacteria have channels to transport ions and other substances Bacteria have membrane proteins to produce energy Bacteria translocate proteins to sense the enviroment: chemotaxis, stress.

5. Co-translational translocation Post-translational translocation

6. Chaperone:1.a person, usually a married or older woman, who, for propriety, accompanies a young unmarried woman in public or who attends a party of young unmarried men and women. 2.any adult present in order to maintain order or propriety at an activity of young people, as at a school dance.

7. Molecular chaperones The term "molecular chaperone" is applied to proteins that control the proper folding of nascent polypeptides into the correct 3D structure) or maintain polypeptides in an inactive state until they have been transported to their ultimate intracellular or extracellular destinations and assembled into functional multiprotein complexes. Molecular chaperones prevent inappropriate interactions that would result in misfolding or mislocation of proteins.

8. In any case, translocation is initiated by the recognition of a peptide, often (but not always) located at the N-terminus of the protein that will be translocated…. recognition site for signal peptidase signal peptide mature protein C N pre protein

9. Protein translocation into the periplasm

10. the Sec system

11. Translocation of proteins into the periplasm by the Sec system 1 2 3

13. The Sec system is necessary for translocation of proteins into the periplasm and can also participate in integration of proteins in the cell membrane

15. Biogenesis of inner membrane proteins

16. Protein translocation into the periplasm

19. Translocation of fully folded GFP by the Tat system: gfp cannot fold properly in the periplasm

22. Translocated using the Tat system

23. The process we have studied are homologous to processes found in eukaryotes