The catalytic sector f 1, with subunits a, b, g, d, and e. C h e m i o s m o s i s a t p s y n th e s i s i n c h l. The resulting acidification of the lumen regulates both light harvesting, via the qe mechanism, and photosynthetic electron transfer through the cytochrome b6f complex. The protondriven atp synthase is embedded in a proton tightcoupling membrane.
The chloroplast atp synthase cf 1f o is located in the stroma lamellae and flat grana end membranes 11. It has long been known that the chloroplast atp synthase is regulated by modulation of a cysteine pair located in a regulatory loop in. Energy conservation occurs across the thylakoid membranes, and light causes the translocation of protons into the internal thylakoid space usually called the lumen. The features of atp synthase nanomachines are remarkably similar in chloroplasts and mitochondria, considering their evolutionary distance of a billion years or more. The chloroplast atp synthase is part of the thylakoid membrane and is orientated with its knobs on the stromal face of the membrane. Atp synthase, enzyme structure, electron microscopy the structure of the atp synthase, f0f, from spinach chloroplasts and beef heart mitochondria has been investigated by electron microscopy with negatively stained specimens.
Structure and function of mitochondrial membrane protein. Experiment showing rotation of atp synthase complex. The properties and the role of chloroplast atpase noncatalytic sites. An overview of the function, composition and structure of. Significance of the subunit in the thiol modulation of chloroplast atp synthase. Structure of the atpsynthase from chloroplasts and. Arrangement of photosystem ii and atp synthase in chloroplast membranes of spinach and pea w oa bertram daum,a daniela nicastro,b jotham austin ii,c j. Chemiosmosis the mechanism of atp synthesis in chloroplasts the thylakoid membrane is composed of a phospholipid bilayer color phospholipids b light blue and photosystem i and photosystem ii.
Pdf on the structure of the atpsynthase from chloroplasts. In the chloroplast stroma 12 hydrogen atoms delivered by12 nadph are bonded with 6 co 2 gas molecules to build a glucose sugar molecule. The wheat chloroplast gene for cf 0 subunit i of atp synthase contains a large intron. It consists of two main subunits, f o and f 1, which has a rotational motor mechanism allowing for atp production. Dye removal, catalytic activity and 2d crystallization of. Thiol modulation of the chloroplast cf0cf1atp synthase atp synthase 2 the chloroplast atp synthase is structurally assigned to a chlo drives the reversible synthesis of atp from adp and pi. The structure and regulation of chloroplast atp synthase. The reaction mechanism of atp synthase has been studied in detail for over half a century. The bulk of atp synthesis in plants is performed by atp synthase, the main bioenergetics engine of cells, operating both in mitochondria and in chloroplasts. Difference in atp synthesis in mitochondria and chloroplast.
Focus on what is needed to start each system and what is produced by each. It was shown that the shortterm incubation of isolated cf 1 in the media with ph 4. The proton atp synthase of thylakoid membranes from spinach chloroplasts cf o f 1 and its subcomplexes cf o and cf 1 were isolated by blue native electrophoresis bnpage neff, d. The structure, activities, and mechanism of the chloroplast atp synthase are discussed. High school and middle school curriculums include cellular respiration labs, photosynthesis experiments, cell energy projects, metabolism activities, photorespiration worksheets, and fermentation exam. The atp synthases are multiprotein complexes found in the energytransducing membranes of bacteria, chloroplasts and mitochondria. Chemiosmosis the mechanism of atp synthesis in chloroplasts. F1f0 atp synthase subunit c is a substrate of the novel yidc pathway for membrane protein biogenesis. Where is the atp synthase located in the chloroplast.
The structure and functional basics of chloroplast atp synthase. Content of rubisco, chl, rieske fes protein of the cyt b 6 f complex, and. Structure, mechanism, and regulation of the chloroplast. A ring of 815 identical csubunits is essential for iontranslocation by the rotary electromotor of the ubiquitous fof1atpase. During photosynthesis in plants, atp is synthesized by atp synthase using a proton gradient created in the thylakoid lumen through the thylakoid membrane and into the chloroplast stroma. Explain how the concentration gradient affects the process of atp synthesis. The atp and nadph generated by chemiosmosis will go into what process of photosynthesis. This is the first documented presence of atp synthase in a supercomplex with the. Ngss life science is a curriculum community for middle school and high school science teachers. Figure4 cryoem structure of the chloroplast atp synthase. The energy for this process is provided by atp created in the light reactions. Pdf expression of the large atp synthase gene cluster in spinach spinacia oleracea chloroplasts is regulated at the posttranscriptional level.
The thylakoid membrane protein cgl160 supports cf1cf0 atp. Get a printable copy pdf file of the complete article 1. Over three billion years, the basic machinery of oxygenic photosynthesis and respiration has been perfected to minimize wasteful reactions. Frontiers chloroplast atp synthase modulation of the.
The gene for cf 0 subunit i of atp synthase has been located in wheat chloroplast dna, between the genes for cf 0 subunit iii and. In the seedlinglethal dpa1 deficiency of plastid atp synthase 1 mutant, absence of detectable amounts of the. Nucleotide sequencing and analysis of rnadna hybrids indicated that the gene is interrupted by an 823bp intron which has boundaries similar to those previously described for the introns in proteincoding chloroplast genes of euglena gracilis. The atp synthase enzyme catalyses the final step of oxidative and photophosphorylation in bacteria, mitochondria and the thylakoids of chloroplasts. On the structure of the atpsynthase from chloroplasts axis the smaller dimension is found and the dimension per pendicular to the string axis. Both processes are accomplished by multicomponent molecular machineries that include a number of dynaminrelated gtpases 9, 10. Atp synthase is likewise a key enzyme of cell respiration. Although they both work simultaneously, it is best to look at them one at a time, starting with photosystem ii. Electron transport chain etc, which takes place in the mitochondria is called oxidative phosphorylation, since.
The chloroplast adenosine triphosphate atp synthase is located in the thylakoid membrane and synthesizes atp from adenosine diphosphate and inorganic phosphate at the expense of the electrochemical proton gradient formed by lightdependent electron flow. It is a complex protein with the function of coupling the passage of protons down their electrochemical gradient to the synthesis of atp. We determined the highresolution structure of the complete. In contrast to mitochondrial atp synthase dimers 12, cf 1f o is monomeric and does not bend the membrane 11. Aspects of subunit interactions in the chloroplast atp. A complex between chloroplast coupling factor 1 cf1 and subunit iii of the membranespanning portion of the chloroplast atp synthase cf0, isolated as described in the accompanying paper c. Arabidopsis thaliana purple acid phosphatase 2 atpap2 is a phosphatase dually targeted to the outer membranes of both organelles and it plays a role in the import of selected nuclearencoded proteins into. The chloroplast adenosine triphosphate atp synthase uses the electrochemical proton gradient generated by photosynthesis to produce atp, the energy currency of all cells.
The energy used to produce atp in the light reactions of. Despite the different cring sizes 10 csubunits in bacillus ps3 versus 14 in spinach chloroplasts, the backbone positions of subunits ab 2 from bacillus ps3 overlap with subunits abb from spinach chloroplast atp synthase hahn et al. Reversible phdependent activationinactivation of cf1. The aim of the work was to study the reverse phdependent regulation of the enzymatic activity of the catalytic part of atp synthase ec 3. Molecular motors structure, mechanism, and regulation. Cf0 has four subunits iiv and is embedded within the thylakoid membrane, where it mediates the transfer of protons, generated by photosynthesis, across the membrane. A concise overview of the chloroplast atp synthase is presented, with an emphasis on its functions, regulation, composition, and structure from fluorescence energy transfer mapping. In the cell, they form a tubular network that constantly changes by division and fusion additional file 1. The wheat chloroplast gene for cf0 subunit i of atp. Nucleusencoded protein bfa1 promotes efficient assembly. The electrons provide the energy needed to produce energy throught photphosphorylation as they mover down the electron carrier change. Calvin cycle reactions of photosynthesis in chloroplast stroma.
In wild type plants, decreasing co2 lowers the activity of the chloroplast atp synthase, slowing proton efflux from the thylakoid lumen resulting in buildup of thylakoid proton motive force pmf. The detergentsolubilized atp synthase forms stringlike structures in which the f0 parts are aggregated. A novel chloroplast supercomplex consisting of the atp. It is composed of two rotary motorsgenerators, f o and f 1, which. In the chloroplast, the atp synthase holocomplex is composed of two subcomplexes, cf 0 and cf 1. The thylakoid membrane protein cgl160 supports cf1cf0 atp synthase accumulation in arabidopsis thaliana. Study 26 terms atp synthase, photosynthesis flashcards. The chloroplast atp genes are organized as two operons in plants but not in the green alga, chlamydomonas reinhardtii. Frontiers optimization of atp synthase function in. Chloroplasts and mitochondria are the major atp producing organelles in plant leaves. The hydrogens produced lose electrons, which then enter either cyclic or noncyclic photophosphorylation. Protons conducted through the membraneembedded f o motor drive atp synthesis in the f 1 head by rotary catalysis. Termed chemiosmosis, the diffusion of hydrogen ions through atp synthase provides the energy to produce atp.
Inactivation of the chloroplast atp synthase subunit results in high nonphotochemical fluorescence quenching and altered nuclear gene expression in arabidopsis thaliana s received for publication, august 1, 2003, and in revised form, october 22, 2003. Free fulltext pdf articles from hundreds of disciplines, all in one place. Atp is mainly produced in the mitochondria and is an important enzyme that provides energy for the cell to use through the synthesis of adenosine triphosphate atp. This causes the formation of a proton gradient by which energy is utilized in synthesizing atp with the assistance of the enzyme atp synthase. The nucleotidedependent mechanism of chloroplast atp synthase regulation. Location and nucleotide sequence of the gene for the protontranslocating subunit of wheat chloroplast atp synthase. The thioldependent mechanism of chloroplast atp synthase regulation. It is spatially separated from the watersplitting photosystem ii in the chloroplast grana.