Electron Transfer and Radical Forming Reactions of Methane Monooxygenase

2000 ◽  
pp. 233-277 ◽  
Author(s):  
Brian J. Brazeau ◽  
John D. Lipscomb
Keyword(s):  
Electron Transfer ◽  
Methane Monooxygenase

scholarly journals Electron Transfer Control in Soluble Methane Monooxygenase

2014 ◽  
Vol 136 (27) ◽  
pp. 9754-9762 ◽  
Author(s):  
Weixue Wang ◽  
Roxana E. Iacob ◽  
Rebecca P. Luoh ◽  
John R. Engen ◽  
Stephen J. Lippard
Keyword(s):  
Electron Transfer ◽  
Methane Monooxygenase ◽  
Soluble Methane Monooxygenase

scholarly journals Inhibition of Membrane-Bound Methane Monooxygenase and Ammonia Monooxygenase by Diphenyliodonium: Implications for Electron Transfer

2004 ◽  
Vol 186 (4) ◽  
pp. 928-937 ◽  
Author(s):  
Andrew K. Shiemke ◽  
Daniel J. Arp ◽  
Luis A. Sayavedra-Soto
Keyword(s):  
Electron Transfer ◽  
Methane Monooxygenase ◽  
Methylococcus Capsulatus ◽  
Ammonia Monooxygenase ◽  
Oxidoreductase Activity ◽  
Nadh:Quinone Oxidoreductase ◽  
Membrane Bound ◽  
Quinone Pool

ABSTRACT Diphenyliodonium (DPI) is known to irreversibly inactivate flavoproteins. We have found that DPI inhibits both membrane-bound methane monooxygenase (pMMO) from Methylococcus capsulatus and ammonia monooxygenase (AMO) of Nitrosomonas europaea. The effect of DPI on NADH-dependent pMMO activity in vitro is ascribed to inactivation of NDH-2, a flavoprotein which we proposed catalyzes reduction of the quinone pool by NADH. DPI is a potent inhibitor of type 2 NADH:quinone oxidoreductase (NDH-2), with 50% inhibition occurring at ≈5 μM. Inhibition of NDH-2 is irreversible and requires NADH. Inhibition of NADH-dependent pMMO activity by DPI in vitro is concomitant with inhibition of NDH-2, consistent with our proposal that NDH-2 mediates reduction of pMMO. Unexpectedly, DPI also inhibits pMMO activity driven by exogenous hydroquinols, but with ≈100 μM DPI required to achieve 50% inhibition. Similar concentrations of DPI are required to inhibit formate-, formaldehyde-, and hydroquinol-driven pMMO activities in whole cells. The pMMO activity in DPI-treated cells greatly exceeds the activity of NDH-2 or pMMO in membranes isolated from those cells, suggesting that electron transfer from formate to pMMO in vivo can occur independent of NADH and NDH-2. AMO activity, which is known to be independent of NADH, is affected by DPI in a manner analogous to pMMO in vivo: ≈100 μM is required for 50% inhibition regardless of the nature of the reducing agent. DPI does not affect hydroxylamine oxidoreductase activity and does not require AMO turnover to exert its inhibitory effect. Implications of these data for the electron transfer pathway from the quinone pool to pMMO and AMO are discussed.

Electron-Transfer Reactions of the Reductase Component of Soluble Methane Monooxygenase fromMethylococcus capsulatus(Bath)†

Biochemistry ◽  
2001 ◽  
Vol 40 (49) ◽  
pp. 14932-14941 ◽  
Author(s):  
Daniel A. Kopp ◽  
George T. Gassner ◽  
Jessica L. Blazyk ◽  
Stephen J. Lippard
Keyword(s):  
Electron Transfer ◽  
Methane Monooxygenase ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
Soluble Methane Monooxygenase

A light optical diffractometer for electron microscopical images operating in line

1978 ◽  
Vol 36 (1) ◽  
pp. 86-87
Author(s):  
P. Bonhomme ◽  
A. Beorchia
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Electron Microscope ◽  
Image Converter ◽  
Coherent Light ◽  
Spatial Filters ◽  
Electron Image ◽  
Electron Microscopical ◽  
Working Parameters ◽  
Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

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