scholarly journals Investigations into the effect of acid on the spectral and kinetic properties of purple membrane from Halobacterium halobium

1980 ◽  
Vol 189 (3) ◽  
pp. 413-420 ◽  
Author(s):  
M E Edgerton ◽  
T A Moore ◽  
C Greenwood
Keyword(s):  
Kinetic Parameters ◽  
Conformational Change ◽  
Reducing Agents ◽  
Purple Membrane ◽  
Buffering Capacity ◽  
Kinetic Properties ◽  
Halobacterium Halobium ◽  
Spectral Changes ◽  
Temporal Placement ◽  
Ph Range

The formation and reversal of the acid species of purple membrane generated below pH 4.00 (22 degrees C) is studied together with the photochemical cycle over the pH range 6.40–3.20. The buffering capacity of the membrane reaches a peak at pH 4.30, indicating the possibility of a conformational change taking place. The generation of the new spectral species can take place in the dark and is unaffected by the addition of reducing agents. Kinetic parameters measured indicate that the group being titrated below pH 4.00 could be the same as that protonated in the formation of intermediate O. The temporal placement of intermediate O after M in the photochemical cycle is shown to be incompatible with the data presented here. Reneutralization of acidified purple membrane shows that the spectral changes in acid are reversible but the phototransient properties are altered.

scholarly journals Studies of an acid-induced species of purple membrane from Halobacterium halobium

1978 ◽  
Vol 171 (2) ◽  
pp. 469-476 ◽  
Author(s):  
T A Moore ◽  
M E Edgerton ◽  
G Parr ◽  
C Greenwood ◽  
R N Perham
Keyword(s):  
Phase Transition ◽  
New Species ◽  
Temperature Dependence ◽  
Ph Dependence ◽  
Low Ph ◽  
Purple Membrane ◽  
Halobacterium Halobium ◽  
Temperature Dependent ◽  
Ph Range ◽  
Increasing Temperature

A new spectral species of the purple membrane of Halobacterium halobium has been observed below pH 3.2. The formation of this new species is temperature-dependent and is favoured by increasing temperature up to the physiological range of the organism. The rate of formation at pH 3.0 and 22 degrees C is 7.9 × 10-3s-1. The spectral distribution and temperature-dependence of the new species suggest that it may be phototransiet O, stabilized by low pH. Flash-photolytic experiments in the pH range 7.2-2.7 show a pH-dependence corresponding to the static events and are consistent with a single protonation of bacteriorhodopsin below pH 3.22. These results can also be interpreted in terms of the stabilization of phototransient O at low pH. The temperature-dependence of the formation of the acid-induced species may reflect a relationship with the phase transition of the membrane.

scholarly journals Spectroscopy and energetics of the purple membrane of Halobacterium halobium

FEBS Letters ◽  
1978 ◽  
Vol 91 (1) ◽  
pp. 131-134 ◽  
Author(s):  
David Cahen ◽  
Haim Garty ◽  
S.Roy Caplan
Keyword(s):  
Purple Membrane ◽  
Halobacterium Halobium

Mechanism of activation of renal Na+-K+-ATPase in the rat: effects of potassium loading

1980 ◽  
Vol 238 (4) ◽  
pp. F315-F323 ◽  
Author(s):  
H. J. Rodriguez ◽  
W. C. Hogan ◽  
R. N. Hellman ◽  
S. Klahr
Keyword(s):  
Thyroid Hormones ◽  
Kinetic Parameters ◽  
Enzyme Induction ◽  
Specific Activity ◽  
Rat Kidney ◽  
Enzymatic Reaction ◽  
Kinetic Properties ◽  
Renal Growth ◽  
Hill Coefficients ◽  
Potassium Loading

The mechanism of activation of Na+-K+-ATPase after chronic potassium loading has been investigated in the rat kidney. Potassium loading stimulated the specific activity of Na+-K+-ATPase in the cortex and medulla of the kidney. This effect was not accompanied by a generalized increase in the cellular contents of RNA and proteins and could not be accounted for by an effect of potassium loading on renal growth. Enzyme induction does not appear to be mediated by changes in the endogenous levels of glucocorticoid or thyroid hormones. Evidence obtained from investigation of the partial reactions (Pi intermediate, ouabain-sensitive pNPPase) of the Na+-K+-ATPase enzymatic reaction is consistent with the interpretation that chronic potassium loading in the rat increases the number of enzyme units (Na+ pumps) in the cortex of the kidney. Analysis of the kinetic parameters (Km, K1/2, Vmax, Hill coefficients) of the enzymatic reaction indicates that K+ loading has little or no effect on the kinetic properties (affinity, cooperativity) of the stimulated transport enzyme.

Ultrastructure of purple membrane and cell wall of Halobacterium halobium

1980 ◽  
Vol 70 (2) ◽  
pp. 204-219 ◽  
Author(s):  
Jiro Usukura ◽  
Eichi Yamada ◽  
Fumio Tokunaga ◽  
Toru Yoshizawa
Keyword(s):  
Cell Wall ◽  
Purple Membrane ◽  
Halobacterium Halobium

scholarly journals On the origin of the red emission of light adapted purple membrane of Halobacterium halobium

FEBS Letters ◽  
1977 ◽  
Vol 78 (1) ◽  
pp. 57-60 ◽  
Author(s):  
Tomas Gillbro ◽  
Arnd N. Kriebel ◽  
Urs P. Wild
Keyword(s):  
Purple Membrane ◽  
Halobacterium Halobium ◽  
Red Emission
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