ATP Synthesis in Cell Envelope Vesicles of Halobacterium halobium Driven by Membrane Potential and/or Base-Acid Transition1

The cell envelope of Halobacterium halobium was seen in thin sections of permanganate-fixed cells to consist of one membrane. This membrane appeared mostly as a unit membrane but in a few preparations it resembled a 5-layered compound membrane. The cell envelope of Halobacterium salinarium at high resolution was always seen as a 5-layered structure different in appearance from the apparent compound membrane of H. halobium. The "envelopes" which were isolated in 12.5 per cent NaCl from each organism were indistinguishable from each other in the electron microscope and comprised, in each case, a single unit membrane with an over-all thickness of about 110 A. Some chemical analyses were made of isolated membranes after freeing them from salt by precipitating and washing with trichloroacetic acid. Such precipitated membranes consisted predominantly of protein, with little carbohydrate and no peptido-aminopolysaccharide (mucopeptide). Sectioned whole cells of H. halobium contained intracellular electron-opaque structures of unknown function.

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Activation and Inhibition of ATP Synthesis in Cell Envelope Vesicles of Halobacterium halobium1

The Journal of Biochemistry ◽

10.1093/oxfordjournals.jbchem.a121915 ◽

1987 ◽

Vol 101 (2) ◽

pp. 311-318 ◽

Cited By ~ 19

Author(s):

Yasuo MUKOHATA ◽

Manabu YOSHIDA

Keyword(s):

Cell Envelope ◽

Atp Synthesis

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Succinate alters respiration, membrane potential, and intracellular K+ in proximal tubule

AJP Renal Physiology ◽

10.1152/ajprenal.1988.255.6.f1170 ◽

1988 ◽

Vol 255 (6) ◽

pp. F1170-F1177 ◽

Cited By ~ 1

Author(s):

S. R. Gullans ◽

B. C. Kone ◽

M. J. Avison ◽

G. Giebisch

Keyword(s):

Membrane Potential ◽

Atpase Activity ◽

Ion Transport ◽

Proximal Tubule ◽

Basolateral Membrane ◽

Coupling Efficiency ◽

Atp Synthesis ◽

Dependent Manner ◽

Kinetic Evaluation ◽

Apparent Increase

Succinate, a dicarboxylic acid, is an intermediate in the Krebs cycle that is transported and metabolized by the renal proximal tubule. It is also known to increase proximal tubule transport of phosphate and glucose but not fluid by unknown mechanisms. In the present study, succinate increased proximal tubule respiration in a dose-dependent manner, and a kinetic evaluation indicated that two separate processes were activated. A lower-affinity (Km = 0.9 mM), higher-capacity stimulation (Vmax increase of 49%) was attributed to a decrease in the mitochondrial coupling efficiency. A higher-affinity process (Km = 0.012 mM) was related to an apparent increase in ATP synthesis. The apparent increase in ATP synthesis was not associated with a change in Na+-K+-ATPase activity, however, but rather indicated a 49% increase in ion transport-independent ATP utilization. Basolateral membrane potential hyperpolarized by -7 mV in the presence of succinate, and this was related to an increase in the K+ transference number. Finally, 1 and 5 mM succinate promoted a net cellular uptake of K+, leading to an 11% increase in intracellular K+, which was not the result of an increase in Na+-K+-ATPase activity. Thus the cellular entry and metabolism of succinate promotes multiple changes in ion transport without altering Na+-K+-ATPase activity.

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