Multiwire Gas Proportional Counters: Decrepit Antiques or ClassicPerformers?

Lewis, Robert A.

doi:10.1107/s090904959400693x

Cited by 53 publications

(41 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…SAXS experiments were performed with protein concentrations between 0.3 and 15 mg/ml. X-ray solution scattering data were collected in two sessions with the low angle scattering camera on station 2.1 (20) at the Synchotron Radiation Source, Daresbury, UK using a position-sensitive multiwire proportional counter (21). At the sample-to-detector distance of 2.4 m and the x-ray wavelength of ϭ 1.54 Å, a momentum transfer interval of 0.002 Å Ϫ1 Յ s Յ 0.050 Å Ϫ1 was covered.…”

Section: Fig 2 Experimental Saxs Results For Solutions Of Oxidized mentioning

confidence: 99%

X-ray Scattering Studies of Methylophilus methylotrophus (sp. W3A1) Electron-transferring Flavoprotein

Jones¹,

Basran²,

Sutcliffe³

et al. 2000

Journal of Biological Chemistry

View full text Add to dashboard Cite

Small angle x-ray solution scattering has been used to generate a low resolution, model-independent molecular envelope structure for electron-transferring flavoprotein (ETF) from Methylophilus methylotrophus (sp. W 3 A 1 ). Analysis of both the oxidized and 1-electron-reduced (anionic flavin semiquinone) forms of the protein revealed that the solution structures of the protein are similar in both oxidation states. Comparison of the molecular envelope of ETF from the x-ray scattering data with previously determined structural models of the protein suggests that ETF samples a range of conformations in solution. These conformations correspond to a rotation of domain II with respect to domains I and III about two flexible "hinge" sequences that are unique to M. methylotrophus ETF. The x-ray scattering data are consistent with previous models concerning the interaction of M. methylotrophus ETF with its physiological redox partner, trimethylamine dehydrogenase. Our data reveal that an "induced fit" mechanism accounts for the assembly of the trimethylamine dehydrogenase-ETF electron transfer complex, consistent with spectroscopic and modeling studies of the assembly process. Electron-transferring flavoproteins (ETFs)1 act as physiological electron carriers between degradative enzymes in bacteria and mitochondria and their respective membrane-bound electron transport pathways (1). ETFs are heterodimeric, and they all possess one equivalent of non-covalently bound flavin-adenine dinucleotide (FAD) per ETF dimer, with the exception of ETF from Megasphaera elsdenii, which contains 2 equivalents of FAD per dimer (2). The ETFs from pig, human, Paracoccus denitrificans, and Methylophilus methylotrophus also contain 1 equivalent of AMP per protein dimer (3-6). ETF from M. methylotrophus (sp. W 3 A 1 ) is a highly specific electron carrier that accepts electrons from only one enzyme, trimethylamine dehydrogenase (TMADH) (7). In methylotrophic bacteria, TMADH catalyzes the oxidative demethylation of trimethylamine to dimethylamine and formaldehyde (8). The enzyme enables these organisms to subsist on trimethylamine as their sole source of carbon. M. methylotrophus ETF consists of two subunits with molecular masses of 34 and 29 kDa (9), and it shares considerable sequence identity with bacterial and mammalian ETFs (3, 4). Preliminary crystallographic studies of M. methylotrophus ETF have been reported, but to date no crystallographic structure for the protein is available (10).Mammalian and bacterial ETFs are thought to act as 1-electron carriers, cycling between the oxidized and anionic flavin semiquinone forms. The ETF from M. elsdenii is unusual in that it serves as a 2-electron carrier. ETFs from mammalian sources and P. denitrificans can be reduced (albeit over a long time period) to the dihydroquinone form by reduction with dithionite or during photochemical reduction. M. methylotrophus ETF is readily converted to the semiquinone form in reactions with TMADH or during artificial reduction with dithionite. Further reduction ...

show abstract

Section: Fig 2 Experimental Saxs Results For Solutions Of Oxidized mentioning

confidence: 99%

X-ray Scattering Studies of Methylophilus methylotrophus (sp. W3A1) Electron-transferring Flavoprotein

Jones¹,

Basran²,

Sutcliffe³

et al. 2000

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…SAXS experiments were performed with protein concentrations between 0.3 and 19 mg/ml. X-ray solution scattering data were collected in two sessions with the low-angle scattering camera on station 2.1 (22) at the Synchotron Radiation Source (Daresbury, UK) using a position-sensitive multiwire proportional counter (23). At the sampleto-detector distance of 2.25 m (1.25 m) and the x-ray wavelength of ϭ 1.54 Å, a momentum transfer interval of 0.002…”

Section: Methodsmentioning

confidence: 99%

Protein Dynamics Enhance Electronic Coupling in Electron Transfer Complexes

Chohan¹,

Jones²,

Grossmann³

et al. 2001

Journal of Biological Chemistry

View full text Add to dashboard Cite

“…Solution X-ray Scattering-Small-angle x-ray scattering (SAXS) data of native and imprinted ETF were collected with the low angle scattering camera on station 2.1 (30) at the Synchrotron Radiation Source, Daresbury, UK, using a position-sensitive multiwire proportional counter (31). The sample-to-detector distance of 1.5 m and protein concentrations of approximately 15 mg/ml were chosen to reveal the scattering behavior in the scattering range 0.01 Å Ϫ1 Յ s Յ 0.08 Å Ϫ1 (s is the modulus of the momentum transfer and defined as s ϭ 2 sin ⌰/, where 2⌰ is the scattering angle and ϭ 1.54 Å is the x-ray wavelength).…”

Section: Methodsmentioning

confidence: 99%

Electron Transfer and Conformational Change in Complexes of Trimethylamine Dehydrogenase and Electron Transferring Flavoprotein

Jones¹,

Talfournier²,

Bobrov³

et al. 2002

Journal of Biological Chemistry

View full text Add to dashboard Cite

The trimethylamine dehydrogenase-electron transferring flavoprotein (TMADH⅐ETF) electron transfer complex has been studied by fluorescence and absorption spectroscopies. These studies indicate that a series of conformational changes occur during the assembly of the TMADH⅐ETF electron transfer complex and that the kinetics of assembly observed with mutant TMADH (Y442F/L/G) or ETF (␣R237A) complexes are much slower than are the corresponding rates of electron transfer in these complexes. This suggests that electron transfer does not occur in the thermodynamically most favorable state (which takes too long to form), but that one or more metastable states (which are formed more rapidly) are competent in transferring electrons from TMADH to ETF. Additionally, fluorescence spectroscopy studies of the TMADH⅐ETF complex indicate that ETF undergoes a stable conformational change (termed structural imprinting) when it interacts transiently with TMADH to form a second, distinct, structural form. The mutant complexes compromise imprinting of ETF, indicating a dependence on the native interactions present in the wild-type complex. The imprinted form of semiquinone ETF exhibits an enhanced rate of electron transfer to the artificial electron acceptor, ferricenium. Overall molecular conformations as probed by smallangle x-ray scattering studies are indistinguishable for imprinted and non-imprinted ETF, suggesting that changes in structure likely involve confined reorganizations within the vicinity of the FAD. Our results indicate a series of conformational events occur during the assembly of the TMADH⅐ETF electron transfer complex, and that the properties of electron transfer proteins can be affected lastingly by transient interaction with their physiological redox partners. This may have significant implications for our understanding of biological electron transfer reactions in vivo, because ETF encounters TMADH at all times in the cell. Our studies suggest that caution needs to be exercised in extrapolating the properties of in vitro interprotein electron transfer reactions to those occurring in vivo.Trimethylamine dehydrogenase (TMADH, 1 EC 1.5.99.7) from the methylotrophic bacterium Methylophilus methylotrophus (sp. W 3 A 1 ) is a homodimeric iron-sulfur flavoprotein that forms an electron transfer complex with electron transferring flavoprotein (ETF (1)). Each subunit of TMADH (molecular mass ϳ 83 kDa) contains a covalently linked 6-S-cysteinyl FMN cofactor, a 4Fe-4S center, and a tightly bound ADP of unknown function (2-8). TMADH catalyzes the oxidative demethylation of trimethylamine to form dimethylamine and formaldehyde (Reaction 1),The mechanism of enzyme reduction by trimethylamine has been addressed by stopped-flow spectroscopy in wild-type (9 -11) and mutant (12-15) TMADH enzymes and has recently been reviewed (16). Following substrate reduction of TMADH, electrons are transferred sequentially from the FMN cofactor to the 4Fe-4S center and, subsequently, in an interprotein electron transfer reaction to the FAD of ...

show abstract

Multiwire Gas Proportional Counters: Decrepit Antiques or ClassicPerformers?

Cited by 53 publications

References 23 publications

X-ray Scattering Studies of Methylophilus methylotrophus (sp. W3A1) Electron-transferring Flavoprotein

X-ray Scattering Studies of Methylophilus methylotrophus (sp. W3A1) Electron-transferring Flavoprotein

Protein Dynamics Enhance Electronic Coupling in Electron Transfer Complexes

Electron Transfer and Conformational Change in Complexes of Trimethylamine Dehydrogenase and Electron Transferring Flavoprotein

Contact Info

Product

Resources

About