Thylakoid Assembly and Folded Protein Transport by the Tat Pathway

2021 ◽  
Author(s):  
Carole Dabney-Smith
Keyword(s):  
Protein Transport ◽  
Tat Pathway

scholarly journals Protein transport by the bacterial Tat pathway

2014 ◽  
Vol 1843 (8) ◽  
pp. 1620-1628 ◽  
Author(s):  
Roshani Patel ◽  
Sarah M. Smith ◽  
Colin Robinson
Keyword(s):  
Protein Transport ◽  
Tat Pathway

scholarly journals The ten amino acids of the oxygen-evolving enhancer of tobacco is sufficient as the peptide residues for protein transport to the chloroplast thylakoid

2021 ◽  
Author(s):  
Sang Hoon Ma ◽  
Hyun Min Kim ◽  
Se Hee Park ◽  
Seo Young Park ◽  
Thanh Dat Mai ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Transport ◽  
Amino Acid Sequences ◽  
Hydrophobic Core ◽  
Thylakoid Lumen ◽  
Transit Peptides ◽  
Tat Pathway ◽  
Arginine Residues ◽  
Oxygen Evolving

Abstract Key message The thylakoid transit peptide of tobacco oxygen-evolving enhancer protein contains a minimal ten amino acid sequences for thylakoid lumen transports. This ten amino acids do not contain twin-arginine, which is required for typical chloroplast lumen translocation. Abstract Chloroplasts are intracellular organelles responsible for photosynthesis to produce organic carbon for all organisms. Numerous proteins must be transported from the cytosol to chloroplasts to support photosynthesis. This transport is facilitated by chloroplast transit peptides (TPs). Four chloroplast thylakoid lumen TPs were isolated from Nicotiana tabacum and were functionally analyzed as thylakoid lumen TPs. Typical chloroplast stroma-transit peptides and thylakoid lumen transit peptides (tTPs) are found in N. tabacum transit peptides (NtTPs) and the functions of these peptides are confirmed with TP–GFP fusion proteins under fluorescence microscopy and chloroplast fractionation, followed by Western blot analysis. During the functional analysis of tTPs, we uncovered the minimum 10 amino acid sequence is sufficient for thylakoid lumen transport. These ten amino acids can efficiently translocate GFP protein, even if they do not contain the twin-arginine residues required for the twin-arginine translocation (Tat) pathway, which is a typical thylakoid lumen transport. Further, thylakoid lumen transporting processes through the Tat pathway was examined by analyzing tTP sequence functions and we demonstrate that the importance of hydrophobic core for the tTP cleavage and target protein translocation.

scholarly journals Hydrophobic mismatch effect is a key factor in protein transport on the Tat pathway

2021 ◽  
Author(s):  
Binhan Hao ◽  
Wenjie Zhou ◽  
Steven M Theg
Keyword(s):  
Protein Transport ◽  
Bacterial Species ◽  
Plant Mitochondria ◽  
Membrane Integrity ◽  
Critical Threshold ◽  
Hydrophobic Mismatch ◽  
Membrane Bilayer ◽  
E Coli ◽  
Tat Pathway ◽  
Folded Proteins

The twin-arginine translocation (Tat) pathway transports folded proteins across membranes in bacteria, thylakoid, plant mitochondria, and archaea. In most species, the active Tat machinery consists of three independent subunits, TatA, TatB and TatC. TatA and TatB from all bacterial species possess short transmembrane alpha-helices (TMHs), both of which are only fifteen residues long in E. coli. Such short TMHs cause a hydrophobic mismatch between Tat subunits and the membrane bilayer. Here, by modifying the length of the TMHs of E. coli TatA and TatB, we access the functional importance of the hydrophobic mismatch in the Tat transport mechanism. Surprisingly, both TatA and TatB with as few as 11 residues in their respective TMHs are still able to insert into the membrane bilayer, albeit with a decline in membrane integrity. Three different assays, both qualitative and quantitative, were conducted to evaluate the Tat activity of the TMH length mutants. Our experiments indicate that the TMHs of TatA and TatB appear to be evolutionarily tuned to 15 amino acids, with activity dropping off with any modification of this length. We believe our study supports a model of Tat transport utilizing localized toroidal pores that form when the membrane bilayer is thinned to a critical threshold. In this context, the 15-residue length of the TatA and TatB TMHs can be seen as a compromise between the need for some hydrophobic mismatch to allow the membrane to reversibly reach the threshold thinness required for toroidal pore formation, and the permanently destabilizing effect of placing even shorter helices into these energy-transducing membranes.

scholarly journals Two electrical potential–dependent steps are required for transport by the Escherichia coli Tat machinery

2007 ◽  
Vol 179 (1) ◽  
pp. 87-99 ◽  
Author(s):  
Umesh K. Bageshwar ◽  
Siegfried M. Musser
Keyword(s):  
Escherichia Coli ◽  
Protein Transport ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Tat Protein ◽  
Twin Arginine Translocation ◽  
Long Duration ◽  
Tat Pathway ◽  
Transport Assay

The twin-arginine translocation (Tat) pathway in Escherichia coli transports fully folded and assembled proteins across the energy-transducing periplasmic membrane. In chloroplasts, Tat transport requires energy input only from the proton motive force. To elucidate the mechanism and energetics of bacterial Tat protein transport, we developed an efficient in vitro transport assay using TatABC-enriched inverted membrane vesicles and the physiological precursor pre-SufI. We report transport efficiencies of 60–80% for nanomolar pre-SufI concentrations. Dissipation of the pH gradient does not reduce pre-SufI transport efficiency. Instead, pre-SufI transport requires at least two electrical potential (Δψ)–dependent steps that differ in both the duration and minimum magnitude of the required Δψ. The data are consistent with a model in which a substantial Δψ of short duration is required for an early transport step, and in which a small Δψ of long duration is necessary to drive a later transport step.

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