Protein import into chloroplasts

Current Opinion in Plant Biology

Volumn 2, Issue 6, 1999, Pages 471-476

  Keegstra, Kenneth ^a   Froehlich, John E ^a  

^a MICHIGAN STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0033485594     PISSN: 13695266     EISSN: None     Source Type: Journal    
DOI: 10.1016/S1369-5266(99)00021-7     Document Type: Review

References (42)

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3. Chen X., Schnell D.J. Protein import into chloroplasts. Trends Cell Biol. 9:1999;222-227.
4. Keegstra K., Cline K. Protein import and routing systems of chloroplasts. Plant Cell. 11:1999;557-570.
5. Schnell D.J. Protein targeting to the thylakoid membrane. Annu Rev Plant Physiol Plant Mol Biol. 49:1998;97-126.
6. Soll J., Tien R. Protein translocation into and across the chloroplastic envelope membranes. Plant Mol Biol. 38:1998;191-207.
7. Schnell D.J., Blobel G., Keegstra K., Kessler F., Ko K., Soll J.A. consensus nomenclature for the protein-import components of the chloroplast envelope. Trends Cell Biol. 7:1997;303-304.
8. Chen K., Chen X., Schnell D.J. The roles of the Toc GTPases in protein import into chloroplasts. Plant Phys. 2000;. in press. The authors demonstrate that Toc86 results from the proteolysis of a native 159 kDa protein, designated Toc159. In addition, when the GTPase domain of Toc159 was selectively removed by controlled proteolysis, binding of precursor protein was reduced significantly while translocation through the protein-conducting channel was reduced but not abolished. Nevertheless, translocation still remains sensitive to GTP analogs even in the absence of the Toc159 GTP-binding domain, suggesting that Toc34 may play a critical role in regulating translocation by GTP.
9. Young M.E., Keegstra K., Froehlich J.E. GTP promotes formation of early import intermediates but is not required during the translocation step of protein import into chloroplasts. Plant Physiol. 121:1999;237-244. Chromatographically purified GTP analogs were used to examine the need for GTP hydrolysis during early and late stages of protein import. The authors demonstrate that GTP hydrolysis is important during the events leading to the formation of early-import intermediates, but GTP does not play a role during the translocation of precursors from the intermediate state.
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13. Akita M., Nielsen E., Keegstra K. Identification of protein transport complexes in the chloroplastic envelope membranes via chemical cross-linking. J Cell Biol. 136:1997;983-994.
14. Ma Y.K., Kouranov A., LaSala S.E., Schnell D.J. Two components of the chloroplast protein import apparatus, IAP86 and IAP75, interact with the transit sequence during the recognition and translocation of precursor proteins at the outer envelope. J Cell Biol. 134:1996;315-327.
15. Nielsen E., Akita M., Davila-Aponte J., Keegstra K. Stable association of chloroplastic precursors with protein translocation complexes that contain proteins from both envelope membranes and a stromal Hsp100 molecular chaperone. EMBO J. 16:1997;935-946.
16. Pinnaduwage P., Bruce B.D. In vitro interaction between a chloroplast transit peptide and chloroplast outer envelope lipids is sequence-specific and lipid class-dependent. J Biol Chem. 271:1996;32907-32915.
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18. Chen L.J., Li H.M. A mutant deficient in the plastid lipid DGD is defective in protein import into chloroplasts. Plant J. 16:1998;33-39. Chloroplasts isolated from an Arabidopsis mutant deficient in digalactosyldiacylglycerol (DGD), were shown to be defective in importing precursor proteins into chloroplasts. The defect in these chloroplasts appears to occur at the energy-independent binding stage of import. This genetic approach provides supporting evidence for the importance of chloroplastic lipids in the precursor import.
19. Kouranov A., Schnell D.J. Analysis of the interactions of preproteins with the import machinery over the course of protein import into chloroplasts. J Cell Biol. 139:1997;1677-1685.
20. Perry S.E., Keegstra K. Envelope membrane proteins that interact with chloroplastic precursor proteins. Plant Cell. 6:1994;93-105.
21. Hirsch S., Muckel E., Heemeyer F., von Heijne G., Soll J. A receptor component of the chloroplast protein translocation machinery. Science. 266:1994;1989-1992.
22. Kessler F., Blobel G., Patel H.A., Schnell D.J. Identification of two GTP-binding proteins in the chloroplast protein import machinery. Science. 266:1994;1035-1039.
23. Seedorf M., Waegemann K., Soll J.A. constituent of the chloroplast import complex represents a new type of GTP-binding protein. Plant J. 7:1995;401-411.
24. Bölter B., May T., Soll J. A protein import receptor in pea chloroplasts, Toc86, is only a proteolytic fragment of a larger polypeptide. FEBS Lett. 441:1998;59-62.
25. Tranel P.J., Froehlich J., Goyal A., Keegstra K.A. component of the chloroplastic protein import apparatus is targeted to the outer envelope membrane via a novel pathway. EMBO J. 14:1995;2436-2446.
26. Hinnah S.C., Hill K., Wagner R., Schlicher T., Soll J. Reconstitution of a chloroplast protein import channel. EMBO J. 16:1997;7351-7360.
27. Jarvis P., Chen L.J., Li H.M., Pete C.A., Fankhauser C., Chory J. An Arabidopsis mutant defective in the plastid general protein import apparatus. Science. 282:1998;100-103. A T-DNA tagged mutant that showed delayed greening led to the identification of Toc33, a translocation component closely related to Toc34. Although the two genes are functionally interchangeable they have different patterns of expression, with Toc33 being preferentially expressed early in seedling development. Chloroplasts from Toc33 mutant plants have a reduced capacity to import precursors and at least one precursor, NADPH:protochlorophyllide oxidoreductase (POR), accumulates in vivo in mutant plants.
28. Schnell D.J., Kessler F., Blobel G. Isolation of components of the chloroplast protein import machinery. Science. 266:1994;1007-1012.
29. Kessler F., Blobel G. Interaction of the protein import and folding machineries in the chloroplast. Proc Natl Acad Sci USA. 93:1996;7684-7689.
30. Lübeck J., Soll J., Akita M., Nielsen E., Keegstra K. Topology of IEP110, a component of the chloroplastic protein import machinery present in the inner envelope membrane. EMBO J. 15:1996;4230-4238.
31. Jackson D.T., Froehlich J.E., Keegstra K. The hydrophilic domain of Tic110, an inner envelope membrane component of the chloroplastic protein translocation apparatus, faces the stromal compartment. J Biol Chem. 273:1998;16583-16588.
32. Caliebe A., Grimm R., Kaiser G., Lübeck J., Soll J., Heins L. The chloroplastic protein import machinery contains a Rieske-type iron-sulfur cluster and a mononuclear iron-binding protein. EMBO J. 16:1997;7342-7350.
33. Kouranov A., Chen X.J., Fuks B., Schnell D.J. Tic20 and Tic22 are new components of the protein import apparatus at the chloroplast inner envelope membrane. J Cell Biol. 143:1998;991-1002. Expanding upon the label-transfer cross-linking approach of Kouranov and Schnell [19] and Perry and Keegstra [20], the authors investigated the interaction of a precursor protein with the chloroplastic protein import apparatus. The authors identified two new components of the import apparatus, Tic22 and Tic20, that are involved in protein translocation across the inner membrane. cDNA clones were isolated for two new import components from the inner envelope membrane. Tic20 is an integral membrane protein and may form part of the protein translocating channel in the inner envelope membrane. Tic22 is a peripheral membrane protein associated with the outer surface of the inner envelope membrane and may be involved in the formation of contact sites.
34. Reumann S., Keegstra K. The endosymbiotic origin of the protein import machinery from chloroplastic envelope membranes. Trends Plant Sci. 8:1999;302-307. Sequence analysis programs were used to identify putative homologs of genes encoding protein import components in a cyanobacterial genome. Because not all components have homologs in cyanobacteria, the authors argue that the import apparatus has a dual origin with some components being inherited from cyanobacteria and other components arising from other origins, probably during the evolutionary pathway leading to modern chloroplasts.
35. Marshall J.S., DeRocher A.E., Keegstra K., Vierling E. Identification of heat shock protein Hsp70 homologues in chloroplasts. Proc Natl Acad Sci USA. 87:1990;374-378.
36. Schirmer E.C., Glover J.R., Singer M.A., Lindquist S. Hsp100/Cpl proteins: A common mechanism explains diverse functions. Trends Biochem Sci. 21:1997;289-296.
37. Ko K., Bornemisza O., Kourtz L., Ko Z.W., Plaxton W.C., Cashmore A.R. Isolation and characterization of a cDNA clone encoding a cognate 70-kDa heat shock protein of the chloroplast envelope. J Biol Chem. 267:1992;2986-2993.
38. Kourtz L., Ko K. The early stage of chloroplast protein import involves Com70. J Biol Chem. 272:1997;2808-2813.
39. Richter S., Lamppa G.K.A. chloroplast processing enzyme functions as the general stromal processing peptidase. Proc Natl Acad Sci USA. 95:1998;7463-7468.
40. Wan J.X., Bringloe D., Lamppa G.K. Disruption of chloroplast biogenesis and plant development upon down-regulation of a chloroplast processing enzyme involved in the import pathway. Plant J. 15:1998;459-468. Plants containing the gene for the chloroplast processing enzyme in an antisense orientation had reduced levels of this protein and reduced levels of the processing enzyme activity. These plants had severe phenotypes including chlorotic leaves, stunted growth, reduced numbers of chloroplasts and aberrant chloroplast morphology. Chloroplasts isolated from these plants had severely reduced ability to import precursors, thereby implicating the processing enzyme directly in the import process.
41. ••] provide the first evidence that one of the chloroplastic protein import components was derived from the cyanobacterial ancestor of chloroplasts.
42. ••], these data provide the first evidence that at least portions of the chloroplastic protein import apparatus was derived from a cyanobacterial ancestor.