Nucleolo Retículo endoplásmico rugoso Retículo endoplásmico liso Vesículas de Golgi Vesículas pequeñas Membrana plasmática...
 
 
 
 
Polipéptidos sintetizados nuevos  en la membrana y asociados a RER <ul><li>Formación de enlaces disulfuro </li></ul><ul><l...
<ul><li>Proteínas correctamente plegadas/armadas  </li></ul><ul><li>RER ⇒ Complejo Golgi  ⇒ Superficie celular u otros </l...
Proteína   Disulfuro  Isomerasa PDI
<ul><li>Principal molécula tiólica en eucariotas </li></ul><ul><li>Impide formación de enlaces disulfuro en citoplasma </l...
 
 
 
 
 
 
13 – 36  residuos  hidrofóbicos
 
Type I:  Signal sequence on amino terminus enters first and continues to elongate. Protein is threaded through the translo...
Type II:  No cleavable signal sequence.  These proteins have rather long hydrophobic regions that will be anchored in the ...
The &quot;positive inside rule&quot; states that amino acid residues nearest the cytosolic side of the hydrophobic anchor ...
Washburn and Speiss (JCB 137: 555-562, 1997) also tested the length of the hydrophobic signal anchor sequence. The followi...
 
 
N –  N-Acetilglucosamina
S –T (OH)  N-Acetil-galactosamina OH-K Galactosa
 
 
 
 
 
 
 
Cis-Golgi
 
The congenital disorders of glycosilation (CDG) were originally called carbohydrate-deficient glycoprotein syndromes (CDGS...
 
 
 
 
Catepsina D y otras enzimas lisozomales
 
 
 
 
 
 
 
 
RER 3 min Aparatp  de Golgi 20 min Vesículas secretoras 90 min Liberación 120 min Páncreas tritio* Radio-autografía
 
RER Cis - Golgi    Fijación grupo fosfato a manosas en enzimas lisosómicas evita que sufran nuevos cambios    Remueve ma...
Medial - Golgi    Remueve manosas por manosidasas I y II     adiciona N-acetilglucosamina por  N-acetil-glucosamina tran...
Trans - Golgi    Completa la gricosilación, adición de  galactosa y ácido siálico (transferasas)     O-oligosacaridos (S...
 
 
 
 
 
 
Acetilacion
The chemical conversion of arginine to citrulline, known as citrullination or deimination.  These citrulline residues are ...
 
 
Certain proteins are anchored to biological membranes by lipid anchors. Particularly common are the N-myristoyl – and S-pa...
Some proteins have lipid moieties attached: The viral  src  protein is  myristoylated  at the N-terminal glycine.  Rhodopo...
Proteins containing the C-terminal sequence  CAAX  can undergo  prenylation  reactions that place thioether-linked  farnes...
The glycosyl phosphatidylinositol  (GPI) moiety is an elaborate lipid-anchoring group. Note the core of three mannose resi...
 
A two dimensional representation of the Human Aquaporin 0 (AQP0) structure indicating sites of truncation (arrows), sites ...
Chymotrypsin and trypsin are both synthesized as  zymogens . Cleavage of chymotrypsinogen between Arg15 and Ile 16 by tryp...
Proteins that require a prosthetic group for activity must have this group added. For example, the haem (heme) group must ...
 
 
 
 
 
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Tema 6 Modificaciones postraduccionales

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Tema 6 Modificaciones postraduccionales

  1. 1. Nucleolo Retículo endoplásmico rugoso Retículo endoplásmico liso Vesículas de Golgi Vesículas pequeñas Membrana plasmática Mitocondria Centriolos Ribosomas Filamentos del citoesqueleto . . . . . . . . . . . . . Peroxisoma Núcleo . . . . Lisosomas .
  2. 6. Polipéptidos sintetizados nuevos en la membrana y asociados a RER <ul><li>Formación de enlaces disulfuro </li></ul><ul><li>Plegamiento adecuado </li></ul><ul><li>Adición y procesamiento de CHOs </li></ul><ul><li>Escisiones proteolíticas específicas </li></ul><ul><li>Formación complejo multimérico </li></ul>
  3. 7. <ul><li>Proteínas correctamente plegadas/armadas </li></ul><ul><li>RER ⇒ Complejo Golgi ⇒ Superficie celular u otros </li></ul><ul><li>No plegadas o plegadas incorrectamente o </li></ul><ul><li>parcialmente plegadas o armadas </li></ul><ul><li>Retenidas con selectividad en RER o </li></ul><ul><li>recuperadas desde CIS-Golgi </li></ul><ul><li>Mal plegadas o armadas </li></ul><ul><li>Retornan del RER a citosol ⇒ degradadas proteasoma </li></ul>
  4. 8. Proteína Disulfuro Isomerasa PDI
  5. 9. <ul><li>Principal molécula tiólica en eucariotas </li></ul><ul><li>Impide formación de enlaces disulfuro en citoplasma </li></ul>GSH:GSSG 50 : 1 NADPH + H + + GSSG ⇒ NADP + + 2 GSH Glutatión reductasa
  6. 16. 13 – 36 residuos hidrofóbicos
  7. 18. Type I: Signal sequence on amino terminus enters first and continues to elongate. Protein is threaded through the translocating channel (open area in rer membrane) until a hydrophobic stop sequence is reached. That hydrophobic stop sequence (seen as a hatched region in the protein) is then inserted in the membrane and forms the anchor for that protein. Signal is cleaved by protease inside the lumen.
  8. 19. Type II: No cleavable signal sequence. These proteins have rather long hydrophobic regions that will be anchored in the membrane. Type II proteins are threaded into the lumen with the C terminus leading. Protein continues to be inserted until it reaches the hydrophobic stop signal sequence. Type III: Same as Type II, only the N terminus leads into the lumen.
  9. 20. The &quot;positive inside rule&quot; states that amino acid residues nearest the cytosolic side of the hydrophobic anchor sequence are more positive than those nearest the lumenal side.  So, whichever end has the least positive charges near the signal anchor patch would go into the ER lumen.  One can change the direction of translocation of a protein (reverse it) by mutating the protein and making more positively charged groups near the anchor patch of the other end. Below, the cartoon shows that this can be done to change a Type II protein (COOH end enters ER lumen) to a Type III (which has its amino terminal entering the lumen).
  10. 21. Washburn and Speiss (JCB 137: 555-562, 1997) also tested the length of the hydrophobic signal anchor sequence. The following cartoon shows that a longer hydrophobic anchor sequence (seen as the portion running through the membrane) promotes entry with the amino terminal leading into the lumen.
  11. 24. N – N-Acetilglucosamina
  12. 25. S –T (OH) N-Acetil-galactosamina OH-K Galactosa
  13. 33. Cis-Golgi
  14. 35. The congenital disorders of glycosilation (CDG) were originally called carbohydrate-deficient glycoprotein syndromes (CDGS) and are a subset of genetic defects affecting primarily N-glycan assembly.
  15. 40. Catepsina D y otras enzimas lisozomales
  16. 49. RER 3 min Aparatp de Golgi 20 min Vesículas secretoras 90 min Liberación 120 min Páncreas tritio* Radio-autografía
  17. 51. RER Cis - Golgi  Fijación grupo fosfato a manosas en enzimas lisosómicas evita que sufran nuevos cambios  Remueve manosas de glicoproteínas .  Fija manosas  N-oligosacáridos (N) Red Cis Vesículas de transición
  18. 52. Medial - Golgi  Remueve manosas por manosidasas I y II  adiciona N-acetilglucosamina por N-acetil-glucosamina transferasa I y II
  19. 53. Trans - Golgi  Completa la gricosilación, adición de galactosa y ácido siálico (transferasas)  O-oligosacaridos (S/T/HO-K)  Liberación de proteínas Red Trans Vesículas de transición .
  20. 60. Acetilacion
  21. 61. The chemical conversion of arginine to citrulline, known as citrullination or deimination. These citrulline residues are generated by a family of enzymes called peptidylarginine deiminases (PADs) , which convert arginine into citrulline in a process called citrulination or deimination .
  22. 64. Certain proteins are anchored to biological membranes by lipid anchors. Particularly common are the N-myristoyl – and S-palmitoyl – anchoring motifs shown here . N-Myristoylation always occurs at an N-terminal glycine residue , whereas thioester linkages occur at cysteine residues within the polypeptide chain. G-protein – coupled receptors, with seven transmembrane segments, may contain one (and sometimes two) palmitoyl anchors in thioester linkage to cysteine residues in the C-terminal segment of the protein.
  23. 65. Some proteins have lipid moieties attached: The viral src protein is myristoylated at the N-terminal glycine. Rhodoposin is palmitoylated at a cysteine residue The ras oncogene protein is farnesylated as are some G proteins. Some eukaryotes, notably parasitic protozoa, have glycosylphosphatidylinositol -linked proteins
  24. 66. Proteins containing the C-terminal sequence CAAX can undergo prenylation reactions that place thioether-linked farnesyl or geranylgeranyl groups at the cysteine side chain. Prenylation is accompanied by removal of the AAX peptide and methylation of the carboxyl group of the cysteine residue, which has become the C-terminal residue.
  25. 67. The glycosyl phosphatidylinositol (GPI) moiety is an elaborate lipid-anchoring group. Note the core of three mannose residues and a glucosamine. Additional modifications may include fatty acids at the inositol and glycerol OOH groups.
  26. 69. A two dimensional representation of the Human Aquaporin 0 (AQP0) structure indicating sites of truncation (arrows), sites of deamidation (green residues) and sites of phosphorylation (red diamonds).
  27. 70. Chymotrypsin and trypsin are both synthesized as zymogens . Cleavage of chymotrypsinogen between Arg15 and Ile 16 by trypsin yields the enzymatically active pi-chymotrypsin. Two further proteolytic cleavages catalyzed by chymotrypsin removes the dipeptides Ser14-Arg15 and Thr147-Asn148 to yield alpha-chymotrypsin. Trypsin is activated by the removal of the N-terminal seven amino acids.
  28. 71. Proteins that require a prosthetic group for activity must have this group added. For example, the haem (heme) group must be added to globins and cytochromes; Fe-S clusters must be added to ferredoxins.
  29. 77. Antes Después Antes Después

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