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Intracellular Compartments and Protein Sorting Haixu Tang School of Informatics.

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Presentation on theme: "Intracellular Compartments and Protein Sorting Haixu Tang School of Informatics."— Presentation transcript:

1 Intracellular Compartments and Protein Sorting Haixu Tang School of Informatics

2 The major intracellular compartments of an animal cell

3 Relative Volumes Occupied by the Major Intracellular Compartments INTRACELLULAR COMPARTMENTPERCENTAGE OF TOTAL CELL VOLUME Cytosol54 Mitochondria22 Rough ER cisternae9 Smooth ER cisternae plus Golgi cisternae 6 Nucleus6 Peroxisomes1 Lysosomes1 Endosomes1

4 An electron micrograph

5 Development of plastids

6 Hypothetical schemes for the evolutionary origins of some organelles

7 Four distinct families 1)the nucleus and the cytosol, which communicate through nuclear pore complexes and are thus topologically continuous (although functionally distinct); 2)all organelles that function in the secretory and endocytic pathways, including the ER, Golgi apparatus, endosomes, lysosomes, the numerous classes of transport intermediates such as transport vesicles, and possibly peroxisomes; 3) the mitochondria; 4)the plastids (in plants only).

8 Secretory vs. endocytic pathways

9 Protein traffic

10 Gated transport Transmembrane transport Vesicular transport –membrane-enclosed transport intermediates

11 Sorting sequences

12 Some sorting sequences

13 Prediction of protein sorting Psort web server: –prediction of protein localization sites in cells from their primary amino acid sequence

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16 Construction of Membrane-enclosed Organelles Require Information in the Organelle Itself The information required to construct a membrane- enclosed organelle does not reside exclusively in the DNA that specifies the organelle's proteins. Epigenetic information in the form of at least one distinct protein that preexists in the organelle membrane is also required, and this information is passed from parent cell to progeny cell in the form of the organelle itself. Presumably, such information is essential for the propagation of the cell's compartmental organization, just as the information in DNA is essential for the propagation of the cell's nucleotide and amino acid sequences.

17 Nuclear pore complexes

18 Nuclear Envelope

19 Nuclear lamina Consists of "intermediate filaments", nm thick. These intermediate filaments are polymers of lamin, ranging from kD. A-type lamins are inside, next to nucleoplasm; B-type lamins are near the nuclear membrane (inner). They may bind to integral proteins inside that membrane. The lamins may be involved in the functional organization of the nucleus.

20 Nuclear localization signals (NLSs)

21 Protein import through nuclear pores

22 Possible paths for free diffusion through the nuclear pore complex

23 Nuclear Import / Export Receptors

24 The control of nuclear import during T-cell activation

25 The breakdown and re-formation of the nuclear envelope during mitosis

26 The subcompartments of mitochondria and chloroplasts

27 A signal sequence for mitochondrial protein import

28 Protein translocators in the mitochondrial membra

29 Protein translocation depends on the temperature

30 Protein import by mitochondria

31 Energy required

32 Two plausible models of how mitochondrial hsp70 could drive protein import

33 Protein import from the cytosol into the inner mitochondrial membrane or intermembrane space

34 Translocation of a precursor protein into the thylakoid space of chloroplasts

35 The Endoplasmic Reticulum

36 Free and membrane-bound ribosomes

37 The signal hypothesis

38 The signal-recognition particle (SRP)

39 SRP direct ribosomes to the ER membrane

40 Protein translocation

41 Single-pass transmembrane protein

42 Multipass membrane protein rhodopsin

43 Protein glycosylation in the rough ER

44 The export and degradation of misfolded ER proteins

45 The unfolded protein response in yeast

46 Phospholipid exchange proteins


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