scholarly journals Charge screening by cations affects the conformation of the mitochondrial inner membrane. A study of exogenous NAD(P)H oxidation in plant mitochondria

1981 ◽  
Vol 195 (3) ◽  
pp. 583-588 ◽  
Author(s):  
I M Møller ◽  
J M Palmer
Keyword(s):  
Electron Transport ◽  
Protein Complexes ◽  
Plant Mitochondria ◽  
Lateral Diffusion ◽  
Jerusalem Artichoke ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Cations caused a decrease in the apparent Km and an increase in the Vmax. for the oxidation of exogenous NADH by both Jerusalem-artichoke (Helianthus tuberosus) and Arum maculatum (cuckoo-pint) mitochondria prepared and suspended in a low-cation medium (approximately or equal to 1 mM-K+). In Arum mitochondria the addition of cations caused a much greater stimulation of the oxidation of NAD(P)H via the cytochrome oxidase pathway than via the alternative, antimycin-insensitive, pathway. This shows that cations affected a rate-limiting step in the electron-transport chain at or beyond ubiquinone, the branch-point of electron transport in plant mitochondria. The effects were only dependent on the valency of the cation (efficiency C3+ greater than C2+ greater than C+) and not on its chemical nature, which is consistent with the theory of the diffuse layer. The results are interpreted to show that the screening of fixed negative membrane changes on lipids and protein complexes causes a conformational change in the mitochondrial inner membrane, leading to a change in a rate-limiting step of NAD(P)H oxidation. More specifically, it is proposed that screening removes electrostatic restrictions on lateral diffusion and thus accelerates diffusion-limited steps in electron transport.

scholarly journals Import of proteins into mitochondria

1988 ◽  
Vol 319 (1193) ◽  
pp. 121-126 ◽  
Keyword(s):  
Native Conformation ◽  
Mitochondrial Membranes ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

A mounting body of evidence suggests that cytoplasmically synthesized proteins destined to be imported into the mitochondrial interior must at least partly unfold to penetrate across the mitochondrial membranes. During post-translational import, this unfolding process appears to be a major rate-limiting step. It can be blocked by ligands that stabilize the protein’s native conformation and appears to be accompanied by the cleavage of ATP outside the mitochondrial inner membrane.

Crystallization of protein–protein complexes

2002 ◽  
Vol 35 (6) ◽  
pp. 674-676 ◽  
Author(s):  
Sergei Radaev ◽  
Peter D. Sun
Keyword(s):  
Sparse Matrix ◽  
Protein Complexes ◽  
Data Bank ◽  
Structure Characterization ◽  
Salt Crystallization ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Crystallization Conditions ◽  
The Stability ◽  
Rate Limiting

Crystallizing protein–protein complexes remains a rate-limiting step in their structure characterization. Crystallization conditions for the known protein–protein complexes have been surveyed in both the Protein Data Bank and the BMCD database. Compared with non-complexed proteins, crystallization conditions for protein–protein complexes are less diverse and heavily favor (71%versus27%) polyethylene glycols (PEG) rather than ammonium sulfate or other high-salt crystallization conditions. The results suggest that the stability of protein complexes limits their available crystallization configuration space. Based on the survey, a set of sparse-matrix screen conditions was designed.

scholarly journals Structure-Based Change in the Rate-Limiting Step of Photosynthetic Electron Transport

2019 ◽  
Vol 116 (3) ◽  
pp. 154a
Author(s):  
William A. Cramer ◽  
J. Ness ◽  
S. Saif Hasan ◽  
Katherine Ehringer ◽  
Sejuti Naurin ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

scholarly journals Electrostatic screening stimulates rate-limiting steps in mitochondrial electron transport

1984 ◽  
Vol 223 (3) ◽  
pp. 761-767 ◽  
Author(s):  
I M Møller ◽  
C J Kay ◽  
J M Palmer
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Active Site ◽  
Plant Mitochondria ◽  
Jerusalem Artichoke ◽  
Maximal Activity ◽  
Effective Concentration ◽  
Ph Optimum ◽  
Transport Chain ◽  
Rate Limiting

The effect of electrostatic screening of fixed negative charges on uncoupled mitochondrial electron transport was investigated with substrates with different charge and different sites of donation of electrons to the electron-transport chain of Jerusalem-artichoke (Helianthus tuberosus L.) mitochondria. Duroquinol (neutral substrate) was oxidized with a pH optimum of 7.6-7.8. The addition of cations caused a doubling of Vmax. (order of efficiency C3+ greater than C2+ greater than C+) through electrostatic screening, whereas the Km was unaffected. Screening stimulated (by 150%) the Vmax. for the oxidation of reduced cytochrome c (positive substrate; to O2), but in this case the Km doubled. The Vmax. of the oxidation of exogenous NADH (negative substrate) was also stimulated by screening when the acceptor was O2, but unaffected when duroquinone was the acceptor. In both cases, the Km for NADH was considerably decreased. The effect of screening on the Km for the different substrates can be explained by the changes in the effective concentration of substrate near the active site due to the lowering in the size of the surface potential. The effect of screening on the Vmax. of the different partial processes indicates that increasing the salt concentration of the medium enhances the maximal activity of cytochrome c oxidase. However, the results also point at the existence of other rate-limiting steps, which are affected by screening and may involve ubiquinone, in electron transport in plant mitochondria.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

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