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Component specificity for the thylakoidal Sec and Delta pH-dependent protein transport pathways.

Mori H, Summer EJ, Ma X, Cline K - J. Cell Biol. (1999)

Bottom Line: Antibodies to either Tha4 or Hcf106 inhibited translocation of four known Delta pH pathway substrate proteins, but not of Sec pathway or SRP pathway substrates.This suggests that Tha4 and Hcf106 operate either in series or as subunits of a heteromultimeric complex. cpSecY antibodies inhibited translocation of Sec pathway substrates but not of Delta pH or SRP pathway substrates.These studies provide the first biochemical evidence that Tha4 and Hcf106 are specific components of the Delta pH pathway and provide one line of evidence that cpSecY is used specifically by the Sec pathway.

View Article: PubMed Central - PubMed

Affiliation: Horticultural Sciences and Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, Florida 32611, USA.

ABSTRACT
Prokaryotes and prokaryote-derived thylakoid membranes of chloroplasts share multiple, evolutionarily conserved pathways for protein export. These include the Sec, signal recognition particle (SRP), and Delta pH/Tat systems. Little is known regarding the thylakoid membrane components involved in these pathways. We isolated a cDNA clone to a novel component of the Delta pH pathway, Tha4, and prepared antibodies against pea Tha4, against maize Hcf106, a protein implicated in Delta pH pathway transport by genetic studies, and against cpSecY, the thylakoid homologue of the bacterial SecY translocon protein. These components were localized to the nonappressed thylakoid membranes. Tha4 and Hcf106 were present in approximately 10-fold excess over active translocation sites. Antibodies to either Tha4 or Hcf106 inhibited translocation of four known Delta pH pathway substrate proteins, but not of Sec pathway or SRP pathway substrates. This suggests that Tha4 and Hcf106 operate either in series or as subunits of a heteromultimeric complex. cpSecY antibodies inhibited translocation of Sec pathway substrates but not of Delta pH or SRP pathway substrates. These studies provide the first biochemical evidence that Tha4 and Hcf106 are specific components of the Delta pH pathway and provide one line of evidence that cpSecY is used specifically by the Sec pathway.

Show MeSH
Pea Tha4 is a novel protein related to maize Tha4 and Hcf106. Tha4 is a distinct Hcf106 paralogue with a truncated COOH terminus. The deduced amino acid sequences of Tha4 from pea (psTha4, accession number AF144708), maize (zmTha4, accession number AF145755), and the predicted Arabidopsis Tha4 EST (atTha4, accession number H37534), as well as Hcf106 from maize (zmHcf106, accession number AF027808), and Arabidopsis (atHcf106, accession number AF139188) were aligned by PILEUP (Genetics Computer Group) and the alignment was enhanced by BOXSHADE (http://www.isrec.isb-sib.ch/software/BOX_form.html), which shows identical amino acids boxed in black and related amino acids boxed in gray.
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Figure 1: Pea Tha4 is a novel protein related to maize Tha4 and Hcf106. Tha4 is a distinct Hcf106 paralogue with a truncated COOH terminus. The deduced amino acid sequences of Tha4 from pea (psTha4, accession number AF144708), maize (zmTha4, accession number AF145755), and the predicted Arabidopsis Tha4 EST (atTha4, accession number H37534), as well as Hcf106 from maize (zmHcf106, accession number AF027808), and Arabidopsis (atHcf106, accession number AF139188) were aligned by PILEUP (Genetics Computer Group) and the alignment was enhanced by BOXSHADE (http://www.isrec.isb-sib.ch/software/BOX_form.html), which shows identical amino acids boxed in black and related amino acids boxed in gray.

Mentions: Screening for a pea Hcf106 homologue employed a mixed probe consisting of the maize Hcf106 cDNA and an Arabidopsis cDNA obtained from the EST program (Fig. 1). A nearly full-length pea cDNA was isolated and extended by 5′-RACE. Similar to the Arabidopsis EST, the pea cDNA encodes a protein that is related to Hcf106 in the transmembrane domain and amphipathic helix, but lacks the extended COOH-terminal acidic domain (Fig. 1). Based on sequence comparison, the predicted pea protein is more similar to Tha4, a newly identified maize protein that is related to Hcf106 in sequence and function (Walker, M.B., L.M. Roy, E. Coleman, R. Voelker, and A. Barkan, manuscript submitted for publication), than it is to Hcf106. Accordingly, the pea protein has been designated psTha4. We have now isolated an Arabidopsis cDNA, based on genomic sequence (accession number AB019226), that appears to encode the authentic Hcf106 orthologue (Fig. 1).


Component specificity for the thylakoidal Sec and Delta pH-dependent protein transport pathways.

Mori H, Summer EJ, Ma X, Cline K - J. Cell Biol. (1999)

Pea Tha4 is a novel protein related to maize Tha4 and Hcf106. Tha4 is a distinct Hcf106 paralogue with a truncated COOH terminus. The deduced amino acid sequences of Tha4 from pea (psTha4, accession number AF144708), maize (zmTha4, accession number AF145755), and the predicted Arabidopsis Tha4 EST (atTha4, accession number H37534), as well as Hcf106 from maize (zmHcf106, accession number AF027808), and Arabidopsis (atHcf106, accession number AF139188) were aligned by PILEUP (Genetics Computer Group) and the alignment was enhanced by BOXSHADE (http://www.isrec.isb-sib.ch/software/BOX_form.html), which shows identical amino acids boxed in black and related amino acids boxed in gray.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199744&req=5

Figure 1: Pea Tha4 is a novel protein related to maize Tha4 and Hcf106. Tha4 is a distinct Hcf106 paralogue with a truncated COOH terminus. The deduced amino acid sequences of Tha4 from pea (psTha4, accession number AF144708), maize (zmTha4, accession number AF145755), and the predicted Arabidopsis Tha4 EST (atTha4, accession number H37534), as well as Hcf106 from maize (zmHcf106, accession number AF027808), and Arabidopsis (atHcf106, accession number AF139188) were aligned by PILEUP (Genetics Computer Group) and the alignment was enhanced by BOXSHADE (http://www.isrec.isb-sib.ch/software/BOX_form.html), which shows identical amino acids boxed in black and related amino acids boxed in gray.
Mentions: Screening for a pea Hcf106 homologue employed a mixed probe consisting of the maize Hcf106 cDNA and an Arabidopsis cDNA obtained from the EST program (Fig. 1). A nearly full-length pea cDNA was isolated and extended by 5′-RACE. Similar to the Arabidopsis EST, the pea cDNA encodes a protein that is related to Hcf106 in the transmembrane domain and amphipathic helix, but lacks the extended COOH-terminal acidic domain (Fig. 1). Based on sequence comparison, the predicted pea protein is more similar to Tha4, a newly identified maize protein that is related to Hcf106 in sequence and function (Walker, M.B., L.M. Roy, E. Coleman, R. Voelker, and A. Barkan, manuscript submitted for publication), than it is to Hcf106. Accordingly, the pea protein has been designated psTha4. We have now isolated an Arabidopsis cDNA, based on genomic sequence (accession number AB019226), that appears to encode the authentic Hcf106 orthologue (Fig. 1).

Bottom Line: Antibodies to either Tha4 or Hcf106 inhibited translocation of four known Delta pH pathway substrate proteins, but not of Sec pathway or SRP pathway substrates.This suggests that Tha4 and Hcf106 operate either in series or as subunits of a heteromultimeric complex. cpSecY antibodies inhibited translocation of Sec pathway substrates but not of Delta pH or SRP pathway substrates.These studies provide the first biochemical evidence that Tha4 and Hcf106 are specific components of the Delta pH pathway and provide one line of evidence that cpSecY is used specifically by the Sec pathway.

View Article: PubMed Central - PubMed

Affiliation: Horticultural Sciences and Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, Florida 32611, USA.

ABSTRACT
Prokaryotes and prokaryote-derived thylakoid membranes of chloroplasts share multiple, evolutionarily conserved pathways for protein export. These include the Sec, signal recognition particle (SRP), and Delta pH/Tat systems. Little is known regarding the thylakoid membrane components involved in these pathways. We isolated a cDNA clone to a novel component of the Delta pH pathway, Tha4, and prepared antibodies against pea Tha4, against maize Hcf106, a protein implicated in Delta pH pathway transport by genetic studies, and against cpSecY, the thylakoid homologue of the bacterial SecY translocon protein. These components were localized to the nonappressed thylakoid membranes. Tha4 and Hcf106 were present in approximately 10-fold excess over active translocation sites. Antibodies to either Tha4 or Hcf106 inhibited translocation of four known Delta pH pathway substrate proteins, but not of Sec pathway or SRP pathway substrates. This suggests that Tha4 and Hcf106 operate either in series or as subunits of a heteromultimeric complex. cpSecY antibodies inhibited translocation of Sec pathway substrates but not of Delta pH or SRP pathway substrates. These studies provide the first biochemical evidence that Tha4 and Hcf106 are specific components of the Delta pH pathway and provide one line of evidence that cpSecY is used specifically by the Sec pathway.

Show MeSH