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Topic: Proton motive force

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proton proton chain

proton pumps

proton pump inhibitors

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	Membrane deinsertion of SecA underlying proton motive force-dependent stimulation of protein translocation
		To determine whether PMF stimulates protein translocation by affecting the membrane insertion of SecA, proOmpA translocation and SecA insertion were analyzed in the presence and absence of PMF (Figure 1).
		The 30 kDa fragment level observed with the mutant membrane vesicles in the absence of PMF was similar to that observed with the wild-type membrane vesicles in the presence of PMF.
		As far as translocation-coupled SecA insertion was concerned, PMF and external SecA induced similar extents of SecA deinsertion (Figures 4B and 6B), indicating that the same species of inserted SecA molecules are competent with regard to deinsertion by PMF and external SecA (Figure 7).
	www.nature.com /emboj/journal/v18/n4/full/7591538a.html (7901 words)

	Energizing porters by proton-motive force (Site not responding. Last check: 2007-10-10)
		The presence of relatively high proton concentrations in the ambient solution resulted in the evolution of proton pumps during the dawn of life on earth.
		The existence of proton-motive force enabled the evolution of porters driven by it that are most probably among the more primitive porters in the world.
		The V-ATPases are a novel class of ATP-dependent proton pumps responsible for acidification of intracellular compartments in eukaryotic cells.
	rsb.info.nih.gov /NeuroChem/biomach/proton_porter.html (425 words)

	Proton Motive Force (Site not responding. Last check: 2007-10-10)
		In prokaryotic cells, the protons are transported from the cytoplasm of the bacterium across the cytoplasmic membrane to the periplasmic space located between the cytoplasmic membrane and the cell wall.
		In eukaryotic cells, protons are transported from the matrix of the mitochondria across the inner mitochondrial membrane to the intermembrane space located between the inner and outer mitochondrial membranes (see Fig.
		Proton motive force is also used to transport substances across membranes during active transport and to rotate bacterial flagella.
	www.cat.cc.md.us /courses/bio141/lecguide/unit1/prostruct/pmf/pmf.html (416 words)

	THE ELECTRON TRANSPORT CHAIN
		The proton gradient may be all or partially converted to a charge difference by exchanging potassium ions for protons.
		In eukaryotes the PMF is generated in the mitochomdria or chloroplasts and is all converted to ATP.
		Proton acceptor groups (e.g., -NH2) are present on the rotor-M-ring and anionic groups (e.g., COO-) are located over the exit channels for protons (see diagram).
	www.science.siu.edu /microbiology/micr425/425Notes/07-Respire.html (3207 words)

	Plant Physiology Online: Chemiosmosis in Action
		In plants, proton gradients play a role in transport across the plasma membrane and the tonoplast and drive both transport and ATP synthesis on the inner membranes of chloroplasts and mitochondria.
		The passage of protons along their electric and chemical gradients can be coupled to cellular work because the change in free energy is negative.
		is the proton gradient of electrochemical potential, F is the Faraday constant, ΔE is the membrane potential, R is the gas constant, T is the absolute temperature, and the superscripts "i" and "o" refer to the inside and outside, respectively, of the cell or other membrane-enclosed compartment.
	www.plantphys.net /article.php?ch=t&id=51 (494 words)

	[No title]
		Changes in ionisation and conformation in helix D/loop D, resulting from proton translocation through dll, are thought to be responsible for the changes in affinity of dill for NADP(+) and NADPH that drive the reaction.
		The latter catalyzes the reduction of protons to molecular H-2 in the chloroplast stroma.
		The coupling constant between the rate of free energy availability from PMF and the rate of reduction of H2O2 flux, was found to be 46.4 mol m(-2) s(-1) J(-1) from simulations using a developed model.
	www-u.life.uiuc.edu /labs/crofts/arc-lit/200002/11105008 (5511 words)

	How To Be Completely Comfortable at Extreme pH (Site not responding. Last check: 2007-10-10)
		There is a net force on protons called the proton motive force, which is the sum of the forces from the extracellular-cytosolic concentration gradient and a charge separation.
		When such a proton motive force exists, the cell can let protons into the cell through an ATP synthesis protein, which uses the energy released from the proton movements to create a phosphate bond.
		The vacuoles are acidified using ATP so that the spontaneous release of protons back into the lumen may be used to pump in sucrose (Maathuis and Sanders 1992).
	www.public.asu.edu /~bdegreg/extremepH/homeostasis.html (553 words)

	A Proton Gradient Powers the Synthesis of ATP (Site not responding. Last check: 2007-10-10)
		In addition, from the results obtained by varying the length of the actin filament and mea-suring the rate of rotation, the enzyme appears to operate near 100% efficiency; that is, essentially all of the energy released by ATP hydrolysis is converted into rotational motion.
		The entry of protons into the cytosolic half-channel is further facilitated by the membrane potential of +0.14 V (positive on the cytoplasmic side), which increases the concentration of protons near the mouth of the cytosolic half-channel.
		Such a rotation moves the newly protonated aspartic acid residue into contact with the membrane, moves the charged aspartate residue from contact with the matrix half-channel to the cytosolic half-channel, and moves a different protonated aspartic acid residue from contact with the membrane to the matrix half-channel.
	www.ncbi.nlm.nih.gov /books/bv.fcgi?call=bv.View..ShowSection&rid=stryer.section.2528 (2366 words)

	STUDIES ON THE COUPLING OF MITOCHONDRIAL ELECTRON TRANSPORT BY PROTON MOTIVE FORCE TO ATP SYNTHESIS
		Substances destroying proton concentration gradient remove the driving force for ATP synthesis and active transport processes; therefore, the coupling between the reactions of producing and using energy will be lost.
		Carefully chosen conditions (ionic constituents of medium) permit the study of how proton motive force is used to transport ions across the inner membrane of mitochondria, or to phosphorylate ADP to ATP.
		If, in well-coupled mitochondria, the synthesis of ATP is inhibited by the antibiotic oligomycin, respiration also becomes suppressed, because proton motive force generated by respiration reaches a limit represented by the Gibbs' free energy change of substrate oxidation (and, also, the matrix becomes alkaline).
	www.biokemia.sote.hu /ob_tanag_en/ob_gya_en/ob_biokem_jegyzet_mit_e.htm (2222 words)

	Biochemical Characterization of a Mutationally Altered Protein Translocase: Proton Motive Force Stimulation of the ...
		IMV (lanes 1 to 5) or SecY39 IMV (lanes 6 to 10) in the presence of the PMF.
		Proton transfer is rate-limiting for translocation of precursor proteins by the Escherichia coli translocase.
		A proline residue near the amino terminus of the mature domain of secretory protein lowers the level of the proton motive force required for translocation.
	jb.asm.org /cgi/content/full/185/2/405 (5183 words)

	Proton-motive force stimulates the proteolytic activity of FtsH, a membrane-bound ATP- dependent protease in ...
		PMF is involved in the import and export of various substances,
		PMF affects the dislocation of the PhoA moiety, we examined degradation
		CCCP, carbonyl cyanide-3-chlorophenylhydrazone; DNP, 2,4-dinitrophenol; Foa, subunit a of the proton ATPase; IPTG, isopropyl-
	www.pnas.org /cgi/content/full/99/12/8066 (3011 words)

	Explain the basis of ATP generation in mitochondria and chloroplasts. How does this differ from the Substrate level ...
		In chloroplasts the proton pump is a complex called cytochrome b6-f, which is similar to the cytochrome found in mitochondria.
		The affect of 1 pH unit difference contributes about -60mV to the proton motive force, therefore the electrochemical force produced in each organelle is very similar (-180mV in the chloroplast and -200mV in the mitochondria).
		In the former 1 ATP is synthesised for every four protons that move across the membrane, in the latter 1 ATP is produced for every three protons that are transferred (these numbers are estimates).
	www.coursework.info /i/864.html (942 words)

	Simultaneous measurements of proton motive force, delta pH, membrane potential, and H+/O ratios in intact Escherichia ...
		Simultaneous measurements of proton motive force, delta pH, membrane potential, and H+/O ratios in intact Escherichia coli -- Setty et al.
		Simultaneous measurements of proton motive force, delta pH, membrane potential, and H+/O ratios in intact Escherichia coli
		From 2.5 to 10 microM, the delta pH and the PMF
	www.biophysj.org /cgi/content/abstract/43/3/371 (396 words)

	New Page 1 (Site not responding. Last check: 2007-10-10)
		The proton motive force provides the additional energy required to maintain a relatively constant cytoplasmic composition during growth in a range of extracellular chemical environments.
		The proton motive force is the potential energy derived when a proton passes across a membrane; in prokayotes, the membrane is the cytoplasmic membrane of the cell; in eukaryotes, the membrane may be part of the mitochondrion or chloroplast.
		The free energy may move the cell, maintain ionic or molecular gradients across the membrane, synthesise the anhydride bonds in adenosine triphosphate, or be used for a mix of these processes.
	www.biotechnics.org /1protoplasmexplain.html (182 words)

	Membrane deinsertion of SecA underlying proton motive force-dependent stimulation of protein translocation -- Nishiyama ... (Site not responding. Last check: 2007-10-10)
		force irrespective of the presence or absence of PMF.
		Driessen, A.J. and Wickner, W. Proton transfer is rate-limiting for translocation of precursor proteins by the Escherichia coli translocase.
		Shiozuka, K., Tani, K., Mizushima, S. and Tokuda, H. The proton motive force lowers the level of ATP required for the in vitro translocation of a secretory protein in Escherichia coli.
	embojournal.npgjournals.com /cgi/content/full/18/4/1049 (6900 words)

	Bio. 315 _515@ Towson: Microbial growth (Site not responding. Last check: 2007-10-10)
		The proton motive force is the potential energy that can be derived by passage of a proton across a membrane (mitochondrial membrane of eucaryote cell or cytoplasmic membrane of prokaryote cell).
		Alternatively, cells given a source of ATP may use its anhydride bond energy to create a proton motive force that in turn may be used to move the cell and to maintain chemical gradients.
		Photosynthesis: is similar to respiration in that the reduction of an oxidant via a specific series of electron carriers establishes the proton motive force.
	www.towson.edu /~wubah/medmicro/Growth.htm (2361 words)

	Metabo_LecOut
		In biology frequently an oxidation/reduction reaction involves the addition or removal of a pair of electrons or a pair of electrons and protons or the equivalent of two hydrogen atoms.
		Both of these components makeup what is called an electrochemical gradient across membrane or proton motive force.
		As protons enter cell via ATPase electrochemical energy is dissipated which is used to carry out oxidative phosphorylation (ADP plus inorganic phosphate, in cytosol, to make ATP).
	faculty.washington.edu /jclara/301/M301lecOut/Metabo.html (930 words)

	Bioenergetics of the formyl-methanofuran dehydrogenase and heterodisulfide reductase reactions in Methanothermobacter ... (Site not responding. Last check: 2007-10-10)
		(1) is driven by a sodium motive force (smf) [7,8].
		± 0.05 units), proton motive (pmf ± 12 mV) and sodium motive (smf ± 12 mV) forces of the cells were measured as described in the text.
		to the Mitchell hypothesis, pmf is composed of the membrane
	content.febsjournal.org /cgi/content/full/270/1/66 (4671 words)

	Sodium Ion Cycle in Bacterial Pathogens: Evidence from Cross-Genome Comparisons -- Häse et al. 65 (3): 353 -- ...
		Most bacteria rely on proton motive force as a source of energy for a variety of cellular processes.
		role of proton motive force in the elongation of the flagellar
		Dissipation of the sodium motive force by ionophores,
	mmbr.asm.org /cgi/content/full/65/3/353 (7465 words)

	Institute of Biological Chemistry
		We are focusing on the dual role of the transthylakoid proton gradient, or proton motive force (pmf), which serves a pivotal role in this balancing act, both as a key intermediate in energy conversion, driving the synthesis of ATP, as well as the trigger for initiation of NPQ.
		New research on the structure and function of the ATP synthase and the cytochrome b6f complex, as well as on the nature of the proton motive force, has begun to reveal how pmf balances these two key roles.
		The energy released in this process is used to pump protons, probably via a mechanism called a Q-cycle, which is responsible to producing about 1/3rd of all of the ATP in plants.
	ibc.wsu.edu /research/kramer (1076 words)

	The Chemiosmotic Hypothesis (Site not responding. Last check: 2007-10-10)
		An intact inner mitochondrial membrane, impermeable to protons, is a requirement of such a model.
		The proton gradient and membrane potential are the proton-motive force that is used to drive ATP synthesis.
		Therefore, shining light on this artificial "purple membrane" formed a proton gradient, which was used by the beef heart mitochondrial ATPase to synthesize ATP.
	fig.cox.miami.edu /~cmallery/255/255etc/chemiosm.htm (462 words)

	Biology
		Biology is the natural science that studies the thermal state of no-equilibrium known as Proton Motive Force, which derives from a specific position and movement of the energy (quantum state), and the quasi-stable thermodynamic systems that experience it.
		The proton Motive Force cannot be performed by these particles by the simple reason that they do not possess cell membranes, chloroplasts or mitochondria. If it is so, then, why the viruses are included in the studies of microbiology and Biology in general?
		There are particles smaller than viruses that do not contain nucleic acids, but they self-reproduce; for example, prions, which are fragments of proteins, inorganic substances crystals, the microspheres, etc. These and the viruses are not considered living forms because they do not make any class of transference of energy of an autonomous way, but spontaneously.
	www.biocab.org /Biology.html (3059 words)

	BI481 Lecture 2
		In microbial cells, the proton-motive force is often formed by the action of electron transport.
		Eventually, it would take as much energy to pump out a proton as the amount of energy in the coupled redox reaction, and no more protons would be extruded (-140 to -200 mV).
		ATPases synthesize ATP by using the energy in the proton-motive force.
	methanogens.pdx.edu /boone/courses/BI481/BI481Lec02.html (743 words)

	Using Light Energy to Generate Transmembrane Proton Gradients
		The energy stored in the resulting transmembrane charge-separated state is used to pump protons across the membrane, generating a proton gradient, or proton motive force.
		The bilayer is spanned by triad artificial reaction centers that undergo photoinduced electron transfer to generate a transmembrane charge-separated state.
		A shuttle quinone Qs uses this charge separation to transport protons across the membrane, establishing a proton gradient.
	photoscience.la.asu.edu /Photosyn/faculty/gust/Liposome.htm (259 words)

	Selected Papers (Site not responding. Last check: 2007-10-10)
		This secondary K+ transport results from K+/H+ antiport that is energized by the proton-motive force generated by a primary, H+ transporting plasma membrane V- ATPase.
		Thus the lepidopteran midgut constitutes a well established example of the emerging concept that the proton motive force is an alternative to the classical sodium motive force for the energization of animal plasma membranes.
		Under physiological conditions, it is energized by the voltage component of the proton motive force.
	www.biologie.uni-osnabrueck.de /Tierphysiologie/KHReview.html (216 words)

	Oxidative Phosphorylation (Site not responding. Last check: 2007-10-10)
		ATP is synthesized when protons flow back to the mitochondrial matrix through an enzyme complex.
		Thus, the oxidation of fuels and the phosphorylation of ADP are coupled by a proton gradient across the inner mitochondrial membrane (Figure 18.2).
		Then, this electron-motive force is converted into a proton-motive force and, finally, the proton-motive force is converted into phosphoryl transfer potential.
	www.ncbi.nlm.nih.gov /books/bv.fcgi?rid=stryer.chapter.2484 (475 words)

	Relationship between Intracellular Phosphate, Proton Motive Force, and Rate of Nongrowth Energy Dissipation (Energy ...
		was correlated with an increase in proton motive force (
		ATP hydrolysis is the primary mechanism of proton motive force (
		Energy-spilling reactions of Streptococcus bovis and resistance of its membrane to proton conductance.
	aem.asm.org /cgi/content/full/64/3/976 (2566 words)

	Becker (Site not responding. Last check: 2007-10-10)
		When protons are pumped across the cristae membrane, an electrochemical gradient is formed.
		Calculate the proton motive force, where the Vm = 0.12 V, pH = 2.0 and T = 25ºC. Calculate the Gº' from the proton motive force.
		Be sure to show where NADH and FADH2 donate their electrons, and where proton pumping occurs.
	occawlonline.pearsoned.com /bookbind/pubbooks/becker_awl/chapter98/medialib/chap14d.html (295 words)

	metab
		Proton motive force can also be used as energy source for
		Photoautotrophs: carbon is obtained by carbon dioxide fixation and energy is derived from sunlight.
		Explain how ATP is generated in the bacterial cell including the role of the cell membrane, cytochromes, proton motive force, and ATP synthetase.
	biology.fullerton.edu /biol302/metab.html (1066 words)

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