scholarly journals Maize defective kernel5 is a bacterial tamB homolog required for chloroplast envelope biogenesis

2018 ◽  
Author(s):  
Junya Zhang ◽  
Shan Wu ◽  
Susan K. Boehlein ◽  
Donald R. McCarty ◽  
Gaoyuan Song ◽  
...  
Keyword(s):  
Inorganic Phosphate ◽  
Phosphate Uptake ◽  
Soluble Sugars ◽  
Chloroplast Envelope ◽  
Membrane Biogenesis ◽  
Envelope Membrane ◽  
Plastid Envelope ◽  
Membrane Envelope ◽  
Bacterial Outer Membrane ◽  
Outer Membrane Biogenesis

ABSTRACTChloroplasts are of prokaryotic origin with a double membrane envelope that separates plastid metabolism from the cytosol. Envelope membrane proteins integrate the chloroplast with the cell, but the biogenesis of the envelope membrane remains elusive. We show that the maize defective kernel5 (dek5) locus is critical for plastid membrane biogenesis. Amyloplasts and chloroplasts are larger and reduced in number in dek5 with multiple ultrastructural defects. We show that dek5 encodes a protein homologous to rice SUBSTANDARD STARCH GRAIN4 (SSG4) and E.coli tamB. TamB functions in bacterial outer membrane biogenesis. The DEK5 protein is localized to the chloroplast envelope with a topology analogous to TamB. Increased levels of soluble sugars in dek5 developing endosperm and elevated osmotic pressure in mutant leaf cells suggest defective intracellular solute transport. Both proteomics and antibody-based analyses show that dek5 chloroplasts have reduced levels of chloroplast envelope transporters. Moreover, dek5 chloroplasts reduce inorganic phosphate uptake with at least an 80% reduction relative to normal chloroplasts. These data suggest that DEK5 functions in plastid envelope biogenesis to enable metabolite transport.

scholarly journals Maize defective kernel5 is a bacterial TamB homologue required for chloroplast envelope biogenesis

2019 ◽  
Vol 218 (8) ◽  
pp. 2638-2658 ◽  
Author(s):  
Junya Zhang ◽  
Shan Wu ◽  
Susan K. Boehlein ◽  
Donald R. McCarty ◽  
Gaoyuan Song ◽  
...  
Keyword(s):  
Inorganic Phosphate ◽  
Phosphate Uptake ◽  
Soluble Sugars ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Double Membrane ◽  
Plastid Envelope ◽  
Membrane Envelope ◽  
Bacterial Outer Membrane ◽  
Outer Membrane Biogenesis

Chloroplasts are of prokaryotic origin with a double-membrane envelope separating plastid metabolism from the cytosol. Envelope membrane proteins integrate chloroplasts with the cell, but envelope biogenesis mechanisms remain elusive. We show that maize defective kernel5 (dek5) is critical for envelope biogenesis. Amyloplasts and chloroplasts are larger and reduced in number in dek5 with multiple ultrastructural defects. The DEK5 protein is homologous to rice SSG4, Arabidopsis thaliana EMB2410/TIC236, and Escherichia coli tamB. TamB functions in bacterial outer membrane biogenesis. DEK5 is localized to the envelope with a topology analogous to TamB. Increased levels of soluble sugars in dek5 developing endosperm and elevated osmotic pressure in mutant leaf cells suggest defective intracellular solute transport. Proteomics and antibody-based analyses show dek5 reduces levels of Toc75 and chloroplast envelope transporters. Moreover, dek5 chloroplasts reduce inorganic phosphate uptake with at least an 80% reduction relative to normal chloroplasts. These data suggest that DEK5 functions in plastid envelope biogenesis to enable transport of metabolites and proteins.

Advances in understanding bacterial outer-membrane biogenesis

2006 ◽  
Vol 4 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Natividad Ruiz ◽  
Daniel Kahne ◽  
Thomas J. Silhavy
Keyword(s):  
Outer Membrane ◽  
Membrane Biogenesis ◽  
Bacterial Outer Membrane ◽  
Outer Membrane Biogenesis

scholarly journals Enzymatic product formation impairs both the chloroplast receptor-binding function as well as translocation competence of the NADPH: protochlorophyllide oxidoreductase, a nuclear-encoded plastid precursor protein.

1995 ◽  
Vol 129 (2) ◽  
pp. 299-308 ◽  
Author(s):  
S Reinbothe ◽  
C Reinbothe ◽  
S Runge ◽  
K Apel
Keyword(s):  
Aminolevulinic Acid ◽  
Transit Peptide ◽  
Precursor Protein ◽  
Receptor Protein ◽  
Chloroplast Envelope ◽  
Dependent Manner ◽  
Envelope Membrane ◽  
Chloroplast Transit Peptide ◽  
Plastid Envelope

The key enzyme of chlorophyll biosynthesis in higher plants, the light-dependent NADPH:protochlorophyllide oxidoreductase (POR, EC 1.6.99.1), is a nuclear-encoded plastid protein. Its posttranslational transport into plastids of barley depends on the intraplastidic availability of one of its substrates, protochlorophyllide (PChlide). The precursor of POR (pPOR), synthesized from a corresponding full-length barley cDNA clone by coupling in vitro transcription and translation, is enzymatically active and converts PChlide to chlorophyllide (Chlide) in a light- and NADPH-dependent manner. Chlorophyllide formed catalytically remains tightly but noncovalently bound to the precursor protein and stabilizes a transport-incompetent conformation of pPOR. As shown by in vitro processing experiments, the chloroplast transit peptide in the Chlide-pPOR complex appears to be masked and thus is unable to physically interact with the outer plastid envelope membrane. In contrast, the chloroplast transit peptide in the naked pPOR (without its substrates and its product attached to it) and in the pPOR-substrate complexes, such as pPOR-PChlide or pPOR-PChlide-NADPH, seems to react independently of the mature region of the polypeptide, and thus is able to bind to the plastid envelope. When envelope-bound pPOR-PChlide-NADPH complexes were exposed to light during a short preincubation, the enzymatically produced Chlide slowed down the actual translocation step, giving rise to the sequential appearance of two partially processed translocation intermediates. However, ongoing translocation induced by feeding the chloroplasts delta-aminolevulinic acid, a precursor of PChlide, was able to override these two early blocks in translocation, suggesting that the plastid import machinery has a substantial capacity to denature a tightly folded, envelope-bound precursor protein. Together, our results show that pPOR with Chlide attached to it is impaired both in the ATP-dependent step of binding to a receptor protein component of the outer chloroplast envelope membrane, as well as in the PChlide-dependent step of precursor translocation.

scholarly journals The transit sequence mediates the specific interaction of the precursor of ferredoxin with chloroplast envelope membrane lipids.

1993 ◽  
Vol 268 (6) ◽  
pp. 4037-4042
Author(s):  
R. van't Hof ◽  
W. van Klompenburg ◽  
M. Pilon ◽  
A. Kozubek ◽  
G. de Korte-Kool ◽  
...  
Keyword(s):  
Membrane Lipids ◽  
Specific Interaction ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Chloroplast Envelope Membrane

Mechanism of protein import across the chloroplast envelope

2000 ◽  
Vol 28 (4) ◽  
pp. 485-491 ◽  
Author(s):  
K. Chen ◽  
X. Chen ◽  
D. J. Schnell
Keyword(s):  
Protein Import ◽  
Essential Elements ◽  
Chloroplast Envelope ◽  
Envelope Membrane ◽  
Outer Envelope ◽  
Double Membrane ◽  
Protein Subunits ◽  
Targeting Signals ◽  
Outer Envelope Membrane ◽  
Envelope Membranes

The development and maintenance of chloroplasts relies on the contribution of protein subunits from both plastid and nuclear genomes. Most chloroplast proteins are encoded by nuclear genes and are post-translationally imported into the organelle across the double membrane of the chloroplast envelope. Protein import into the chloroplast consists of two essential elements: the specific recognition of the targeting signals (transit sequences) of cytoplasmic preproteins by receptors at the outer envelope membrane and the subsequent translocation of preproteins simultaneously across the double membrane of the envelope. These processes are mediated via the co-ordinate action of protein translocon complexes in the outer (Toe apparatus) and inner (Tic apparatus) envelope membranes.

Inorganic phosphate uptake in Trypanosoma cruzi is coupled to K+ cycling and to active Na+ extrusion

2013 ◽  
Vol 1830 (8) ◽  
pp. 4265-4273 ◽  
Author(s):  
C.F. Dick ◽  
A.L.A. Dos-Santos ◽  
D. Majerowicz ◽  
L.S. Paes ◽  
N.L. Giarola ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Inorganic Phosphate ◽  
Phosphate Uptake
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