Molecular Dissection of the Mechanism of Protein Import into Chloroplasts

Tian, Feng; Ma, Y.–P.; Kouranov, Andrei; LaSala, S.E.; Schnell, Danny J.

doi:10.1101/sqb.1995.060.01.067

Cited by 1 publication

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(Figure 8) presents an intriguing difference from protein import into mitochondria, in which outer and inner membrane translocation complexes can act independently, and peptidase (for reviews, see Archer and Keegstra, 1990; are only connected by translocating precursors (Segui- Soll and Alefsen, 1993;Tian et al, 1995). This ATP-Real et al, 1993;Horst et al, 1994).…”

Section: Discussionmentioning

confidence: 99%

“…Previous models, showing bound precursors associated only with outer envelope membranes, were based on observations that, in limiting ATP conditions, precursors were not inserted sufficiently into the translocation machinery to be protected from exogenous protease, or to allow cleavage of the transit peptide by stromal processing peptidase (for reviews, see Archer and Keegstra, 1990; Soll and Alefsen, 1993; Tian et al ., 1995). This ATP‐dependent stage of import, where precursors associate stably with chloroplastic membranes, has been termed binding.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, a fraction of ClpC interacts tightly with the chloroplastic envelopes in the absence of precursor, despite the fact that the majority of ClpC is a soluble protein (data not shown). Some of these membrane-bound ClpC proteins interacted with IEP110 and OEP75, and to a lesser degree with ( Figure 8) presents an intriguing difference from protein import into mitochondria, in which outer and inner membrane translocation complexes can act independently, and peptidase (for reviews, see Archer and Keegstra, 1990; are only connected by translocating precursors (Segui-Soll and Alefsen, 1993;Tian et al, 1995). This ATP-Real et al, 1993;Horst et al, 1994).…”

Section: Conditionsmentioning

confidence: 99%

See 2 more Smart Citations

Stable association of chloroplastic precursors with protein translocation complexes that contain proteins from both envelope membranes and a stromal Hsp100 molecular chaperone

et al. 1997

View full text Add to dashboard Cite

NTPs , and results in the irreversible Jennifer Davila-Aponte and interaction of precursors with the chloroplastic envelopes. Kenneth Keegstra 1At this stage, the precursor remains susceptible to exo-MSU-DOE Plant Research Laboratory, Michigan State University, genous protease and the transit peptide is not cleaved East Lansing, MI 48824, USA by the stromal processing peptidase, indicating that the 1 Corresponding author precursor has not completely traversed the envelope membranes (Cline et al., 1985). Translocation of precursors Cytoplasmically synthesized precursors interact with across the envelope membranes can be initiated by raising translocation components in both the outer and inner stromal ATP concentrations (Pain and Blobel, 1987; Theg envelope membranes during transport into chloro et al., 1989). After a precursor has traversed the envelope plasts. Using co-immunoprecipitation techniques, with membranes, the transit peptide is proteolytically removed antibodies specific to known translocation components, by a stromal processing peptidase, producing a maturewe identified stable interactions between precursor sized protein in the stromal compartment (Reed et al., proteins and their associated membrane translocation 1990). components in detergent-solubilized chloroplasticTranslocation of precursors across the two chloroplastic membrane fractions. Antibodies specific to the outer envelope membranes is thought to occur simultaneously envelope translocation components OEP75 and OEP34, at 'contact sites' (Schnell and Blobel, 1993), a term given the inner envelope translocation component IEP110 to regions where both envelope membranes are found in and the stromal Hsp100, ClpC, specifically co-immunoclose physical proximity. By analogy with mitochondria, precipitated precursor proteins under limiting ATP where precursors must also cross two membranes, preconditions, a stage we have called docking. A portion cursors at contact sites are thought to interact with proteinof these same translocation components was coaceous complexes from both the inner and outer immunoprecipitated as a complex, and could also be membranes (for review, see Schatz and Dobberstein, detected by co-sedimentation through a sucrose density 1996). In mitochondria, translocation complexes from the gradient. ClpC was observed only in complexes with outer and inner membranes can act independently from those precursors utilizing the general import apparone another, forming contact sites only when precursors atus, and its interaction with precursor-containing associate with both complexes simultaneously (Segui-Real translocation complexes was destabilized by ATP. et al., 1993;Horst et al., 1995). Whether simultaneous Finally, ClpC was co-immunoprecipitated with a porengagement is required in chloroplasts is presently tion of the translocation components of both outer and unknown. inner envelope membranes, even in the absence of Recent work on the chloroplastic protein import apparadded precursors. We discuss possible roles for stromal atus...

show abstract

Section: Discussionmentioning

confidence: 99%