Tic62: a protein family from metabolism to protein translocation

Balsera, Mónica; Stengel, Anna; Soll, Jürgen; Bölter, Bettina

doi:10.1186/1471-2148-7-43

Cited by 46 publications

(50 citation statements)

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“…4, A-C). Tic62 is proposed to attach to the inner envelope membrane at the stromal face, not exposed to the IMS (8,42), and is, therefore, useful as control for the proteolysis experiments presented here. To control the quenching reaction of the protease adequately, one sample was initially incubated with the proteinase inhibitor mixture prior to adding the protease.…”

Section: Native Tic110 In Iev Is Sensitive To Proteases That Cannot Cmentioning

confidence: 99%

Characterization of Tic110, a Channel-forming Protein at the Inner Envelope Membrane of Chloroplasts, Unveils a Response to Ca2+ and a Stromal Regulatory Disulfide Bridge

Balsera

Goetze

Kovács-Bogdán

et al. 2009

Journal of Biological Chemistry

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117

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Tic110 has been proposed to be a channel-forming protein at the inner envelope of chloroplasts whose function is essential for the import of proteins synthesized in the cytosol. Sequence features and topology determination experiments presently summarized suggest that Tic110 consists of six transmembrane helices. Its topology has been mapped by limited proteolysis experiments in combination with mass spectrometric determinations and cysteine modification analysis. Two hydrophobic transmembrane helices located in the N terminus serve as a signal for the localization of the protein to the membrane as shown previously. The other amphipathic transmembrane helices are located in the region composed of residues 92-959 in the pea sequence. This results in two regions in the intermembrane space localized to form supercomplexes with the TOC machinery and to receive the transit peptide of preproteins. A large region also resides in the stroma for interaction with proteins such as molecular chaperones. In addition to characterizing the topology of Tic110, we show that Ca 2؉ has a dramatic effect on channel activity in vitro and that the protein has a redox-active disulfide with the potential to interact with stromal thioredoxin.After the proposed endosymbiotic event that gave rise to chloroplasts and, as a consequence, to the massive transfer of genes from the endosymbiont to the host cell nucleus, two new machineries were developed at the outer and inner envelope of chloroplasts, the TOC and TIC complexes, respectively. The machineries transport plastid proteins, whose synthesis was moved to the cytosol, back to the plastid (for a review, see Refs. 1 and 2). Whereas the channel of the TOC complex is homologous to the Omp85 family of transporters in bacteria (3), the TIC complex shows no homology to known transport systems, since the plasma membrane-bacterial transport machineries were relocated to the thylakoid membrane. Moreover, there was an essential requirement for establishing new lines of communication between the organelle and other parts of the cell (4). In chloroplasts of land plants, redox regulation is linked to oxygen and/or light. The regulation of chloroplast-specific processes by redox in accord with the status of the organelle applies not only for transcription and translation but also for translocation. Redox regulation at the translocation level has been proposed for the TIC machinery on the basis of protein composition and dynamics (5-8) as well as specific in vitro import experiments (9). However, despite advances in our biochemical understanding of the import process, little is presently known regarding details of the role of redox or of the structure of the TIC complex, particularly with respect to its channel subunits.Tic110 is essential for protein import into plastids (10 -12). It has been proposed to be a pore-forming protein and one of the main components of the TIC complex (13). Previous studies have provided information about certain aspects of Tic110 structure-function. The region from residu...

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Section: Native Tic110 In Iev Is Sensitive To Proteases That Cannot Cmentioning

confidence: 99%

Characterization of Tic110, a Channel-forming Protein at the Inner Envelope Membrane of Chloroplasts, Unveils a Response to Ca2+ and a Stromal Regulatory Disulfide Bridge

Balsera

Goetze

Kovács-Bogdán

et al. 2009

Journal of Biological Chemistry

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117

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“…The specific interaction with FNR is mediated by a conserved sequence motif rich in proline and serine residues, located in the C terminus of Tic62 (2, 3). Interestingly, this motif is restricted to Tic62 proteins from vascular plants (5), and it occurs in different numbers dependent on the respective plants species. Additionally, a second protein containing the Ser/Pro-rich FNR-binding motif has been recently identified in Arabidopsis thaliana and named Trol (thylakoid rhodanese-like protein).…”

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confidence: 99%

Ferredoxin:NADPH oxidoreductase is recruited to thylakoids by binding to a polyproline type II helix in a pH-dependent manner

Alte

Stengel

Benz

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Ferredoxin:NADPH oxidoreductase (FNR) is a key enzyme of photosynthetic electron transport required for generation of reduction equivalents. Recently, two proteins were found to be involved in membrane-anchoring of FNR by specific interaction via a conserved Ser/Pro-rich motif: Tic62 and Trol. Our crystallographic study reveals that the FNR-binding motif, which forms a polyproline type II helix, induces self-assembly of two FNR monomers into a backto-back dimer. Because binding occurs opposite to the FNR active sites, its activity is not affected by the interaction. Surface plasmon resonance analyses disclose a high affinity of FNR to the binding motif, which is strongly increased under acidic conditions. The pH of the chloroplast stroma changes dependent on the light conditions from neutral to slightly acidic in complete darkness or to alkaline at saturating light conditions. Recruiting of FNR to the thylakoids could therefore represent a regulatory mechanism to adapt FNR availability/activity to photosynthetic electron flow.polyproline helix | proline recognition domain | protein-protein interaction | Tic62

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“…These three proline-rich repeats specifically interact with ferredoxin:NADPH oxidoreductase (FNR), an enzyme that catalyses the final step within the electron transfer chain of oxygenic photosynthesis from ferredoxin to NADP, playing an essential role in CO 2 fixation and chloroplast redox-controlled metabolism. A recent study identified Tic62 homologues in a variety of photosynthetic organisms, including not only plants, but also cyanobacteria and even green sulphur bacteria (Balsera et al, 2007). Interestingly, the full-length form of Tic62 was exclusively found in higher plants, whereas all non-vascular plants, including Physcomitrella patens, and all bacterial and algal species contained only a short, truncated form of Tic62 lacking the C-terminal part with the FNR-binding repeats.…”

Section: The Tic Complexmentioning

confidence: 99%

Protein import into chloroplasts: new aspects of a well-known topic

Stengel¹,

Soll²,

Bölter³

2007

BCHM

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Protein import into plant chloroplasts is a fascinating topic that is being investigated by many research groups. Since the majority of chloroplast proteins are synthesised as precursor proteins in the cytosol, they have to be posttranslationally imported into the organelle. For this purpose, most preproteins are synthesised with an Nterminal presequence, which is both necessary and sufficient for organelle recognition and translocation initiation. The import of preproteins is facilitated by two translocation machineries in the outer and inner envelope of chloroplasts, the Toc and Tic complexes, respectively. Translocation of precursor proteins across the envelope membrane has to be highly regulated to react to the metabolic requirements of the organelle. The aim of this review is to summarise the events that take place at the translocation machineries that are known so far. In addition, we focus in particular on alternative import pathways and the aspect of regulation of protein transport at the outer and inner envelope membrane.

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Tic62: a protein family from metabolism to protein translocation

Cited by 46 publications

References 50 publications

Characterization of Tic110, a Channel-forming Protein at the Inner Envelope Membrane of Chloroplasts, Unveils a Response to Ca2+ and a Stromal Regulatory Disulfide Bridge

Characterization of Tic110, a Channel-forming Protein at the Inner Envelope Membrane of Chloroplasts, Unveils a Response to Ca2+ and a Stromal Regulatory Disulfide Bridge

Ferredoxin:NADPH oxidoreductase is recruited to thylakoids by binding to a polyproline type II helix in a pH-dependent manner

Protein import into chloroplasts: new aspects of a well-known topic

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