Chloroplast outer envelope protein P39 in Arabidopsis thaliana belongs to the Omp85 protein family.
Proteins of the Omp85 family chaperone the membrane insertion of β-barrel-shaped outer membrane proteins in bacteria, mitochondria, and probably chloroplasts and facilitate the transfer of nuclear-encoded cytosolically synthesized preproteins across the outer envelope of chloroplasts. This protein family is characterized by N-terminal polypeptide transport-associated (POTRA) domains and a C-terminal membrane-embedded β-barrel. We have investigated a recently identified Omp85 family member of Arabidopsis thaliana annotated as P39. We show by in vitro and in vivo experiments that P39 is localized in chloroplasts. The electrophysiological properties of P39 are consistent with those of other Omp85 family members confirming the sequence based assignment of P39 to this family. Bioinformatic analysis showed that P39 lacks any POTRA domain, while a complete 16 stranded β-barrel including the highly conserved L6 loop is proposed. The electrophysiological properties are most comparable to Toc75-V, which is consistent with the phylogenetic clustering of P39 in the Toc75-V rather than the Toc75-III branch of the Omp85 family tree. Taken together P39 forms a pore with Omp85 family protein characteristics. The bioinformatic comparison of the pore region of Toc75-III, Toc75-V, and P39 shows distinctions of the barrel region most likely related to function. Proteins 2017; 85:1391-1401. © 2014 Wiley Periodicals, Inc.
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.
Yi-Ching
YC
Hsueh
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.|Center of Membrane Proteomics, Goethe University, D-60438, Frankfurt, Germany.
Nadine
N
Flinner
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.
Lucia E
LE
Gross
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.
Raimund
R
Haarmann
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.
Oliver
O
Mirus
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.
Maik S
MS
Sommer
Department of Molecular Cell Biology of Plants, Goethe University, D-60438, Frankfurt, Germany.|Center of Membrane Proteomics, Goethe University, D-60438, Frankfurt, Germany.|Cluster of Excellence Frankfurt, Goethe University, D-60438, Frankfurt, Germany.|Buchman Institute of Molecular Life Sciences, Goethe University, D-60438, Frankfurt, Germany.
Enrico
E
Schleiff
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D019295:Computational Biology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D007425:Intracellular Membranes / Q000737:chemistry* / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D018547:Plant Stems / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000072757:Protein Conformation, beta-Strand; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C532780:OEP80 protein, Arabidopsis; D011994:Recombinant Proteins; C568082:Toc75-III protein, Arabidopsis
Omp85; barrel properties; channel properties; chloroplasts; β-barrel membrane protein