Internal ATP Is The Only Energy Requirement for the Translocation of Precursor Proteins Across Chloroplastic Membranes

Theg, Steven M.; Bauerle, Cynthia; Olsen, Laura J.; Selman, Bruce R.; Keegstra, Kenneth

doi:10.1016/s0021-9258(18)83490-1

Cited by 260 publications

(34 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This suggests that the energy for initial unfolding of the chloroplast precursor provided by the chloroplast translocon is higher than that provided by the mitochondrial one. This might be reconciled taking the hypothesis of the involvement of an inter-membrane space (IMS)-localized Hsp70 into account (Figure 6i and 6ii; Marshall et al, 1990;Schnell et al, 1994;Theg et al, 1989). The observed influence of mutations of the core domain might be explained by the fact that final translocation is energized by a system different from that in mitochondria, namely by the stromal Hsp93 system (ClpC; see Chou et al, 2006;Kovacheva et al, 2007;Oreb et al, 2008).…”

Section: Discussionmentioning

confidence: 91%

“…The translocation process itself can be divided into three energyrequiring steps (Figure 1A): (i) binding of the precursor to the outer envelope membrane, (ii) transport across the outer and inner envelope membrane, and (iii) processing and folding of the translocated proteins in the stroma or thylakoid lumen. Initially, an ATP requirement for all three processes was proposed (Scott and Theg, 1996), and ATP produced by the photosynthetic reaction was found to be sufficient to drive protein translocation (Flu ¨gge and Hinz, 1986;Theg et al, 1989). In contrast to mitochondria, a membrane potential is not required for translocation across the two membranes (Pain and Blobel, 1987).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the Impact of Precursor Unfolding during Protein Import into Chloroplasts

et al. 2010

View full text Add to dashboard Cite

Protein translocation across membranes is a fundamental cellular process. The majority of the proteins of organelles such as mitochondria and chloroplasts is synthesized in the cytosol and subsequently imported in a post-translational manner. The precursor proteins have to be unfolded at least for translocation, but it has also been assumed that they are unfolded during transport to the organelle in the cytosol. Unfolding is governed by chaperones and the translocon itself. At the same time, chaperones provide the energy for the import process. The energetic properties of the chloroplast translocon were studied by import of the Ig-like module of the muscle protein titin fused to the transit peptide of the chloroplast targeted oxygen evolving complex subunit of 33 kDa (OE33). Our results suggest that p(OE33)titin is folded prior to import and that translocation is initiated by unfolding after having bound to the translocon at the chloroplast surface. Using a set of stabilizing and destabilizing mutants of titin previously analyzed by atomic force microscopy and as passenger for mitochondrial translocation, we studied the unfolding force provided by the chloroplast translocon. Based on these results, a model for translocation is discussed.

show abstract

Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

On the Impact of Precursor Unfolding during Protein Import into Chloroplasts

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The transcription reaction was carried out essentially as described (Melton et al, 1984) using 5 t~g of DNA linearized with HindIII. In vitro translation of the mRNA from the transcription reaction was performed using wheat germ lysate as previously described (Theg et al, 1989). Tran3SS-label was substituted for 3H-leucine.…”

Section: In Vitro Synthesis Of Apimentioning

confidence: 99%

Aminopeptidase I of Saccharomyces cerevisiae is localized to the vacuole independent of the secretory pathway.

Klionsky

Cueva

Yaver

1992

The Journal of Cell Biology

353

449

View full text Add to dashboard Cite

Abstract. The Saccharomyces cerevisiae APE1 gene product, aminopeptidase I (API), is a soluble hydrolase that has been shown to be localized to the vacuole. API lacks a standard signal sequence and contains an unusual amino-terminal propeptide. We have examined the biosynthesis of API in order to elucidate the mechanism of its delivery to the vacuole. API is synthesized as an inactive precursor that is matured in a PEP4-dependent manner. The half-time for processing is approximately 45 min. The API precursor remains in the cytoplasm after synthesis and does not enter the secretory pathway, The precursor does not receive glycosyl modifications, and removal of its propeptide occurs in a sec-independent manner. Neither the precursor nor mature form of API are secreted into the extracellular fraction in Ws mutants or upon overproduction, two additional characteristics of soluble vacuolar proteins that transit through the secretory pathway. Overproduction of API results in both an increase in the half-time of processing and the stable accumulation of precursor protein. These results suggest that API enters the vacuole by a posttranslational process not used by most previously studied resident vacuolar proteins and will be a useful model protein to analyze this alternative mechanism of vacuolar localization.

show abstract

“…

chloroplasts (Theg et al, 1989; Keegstra and Cline, 1999). In addition, the electrochemical H ϩ potential (⌬ ˜Hϩ ) of energy conserving membranes contributes to the driving force for protein transport across the bacterial inner membrane (Schiebel et al, 1991;Driessen,

…”

mentioning

confidence: 99%

Energetics of Protein Transport across Biological Membranes

Alder¹,

Theg

2003

Cell

View full text Add to dashboard Cite

Among the pathways for protein translocation across biological membranes, the DeltapH-dependent/Tat system is unusual in its sole reliance upon the transmembrane pH gradient to drive protein transport. The free energy cost of protein translocation via the chloro-plast DeltapH-dependent/Tat pathway was measured by conducting in vitro transport assays with isolated thylakoids while concurrently monitoring energetic parameters. These experiments revealed a substrate-specific energetic barrier to cpTat-mediated transport as well as direct utilization of protons from the gradient, consistent with a H+/protein antiporter mechanism. The magnitude of proton flux was assayed by four independent approaches and averaged 7.9 x 10(4) protons released from the gradient per transported protein. This corresponds to a DeltaG transport of 6.9 x 10(5) kJ.mol protein translocated(-1), representing the utilization of an energetic equivalent of 10(4) molecules of ATP. At this cost, we estimate that the DeltapH-dependent/cpTat pathway utilizes approximately 3% of the total energy output of the chloroplast.

show abstract

Internal ATP Is The Only Energy Requirement for the Translocation of Precursor Proteins Across Chloroplastic Membranes

Cited by 260 publications

References 30 publications

On the Impact of Precursor Unfolding during Protein Import into Chloroplasts

On the Impact of Precursor Unfolding during Protein Import into Chloroplasts

Aminopeptidase I of Saccharomyces cerevisiae is localized to the vacuole independent of the secretory pathway.

Energetics of Protein Transport across Biological Membranes

Contact Info

Product

Resources

About