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Title: Maturation of Hydrogenases

Abstract

Enzymes possessing the capacity to oxidize molecular hydrogen have developed convergently three class of enzymes leading to: [FeFe]-, [NiFe]-, and [FeS]-cluster-free hydrogenases. They differ in the composition and the structure of the active site metal centre and the sequence of the constituent structural polypeptides but they show one unifying feature, namely the existence of CN and/or CO ligands at the active site Fe. Recent developments in the analysis of the maturation of [FeFe]- and [NiFe]- hydrogenases have revealed a remarkably complex pattern of mostly novel biochemical reactions. Maturation of [FeFe]-hydrogenases requires a minimum of three auxiliary proteins, two of which belong to the class of Radical-SAM enzymes and other to the family of GTPases. They are sufficient to generate active enzyme when their genes are co-expressed with the structural genes in a heterologous host, otherwise deficient in [FeFe]-hydrogenase expression. Maturation of the large subunit of [NiFe]-hydrogenases depends on the activity of at least seven core proteins that catalyze the synthesis of the CN ligand, have a function in the coordination of the active site iron, the insertion of nickel and the proteolytic maturation of the large subunit. Whereas this core maturation machinery is sufficient to generate active hydrogenase in themore » cytoplasm, like that of hydrogenase 3 from Escherichia coli, additional proteins are involved in the export of the ready-assembled heterodimeric enzyme to the periplasm via the twin-arginine translocation system in the case of membrane-bound hydrogenases. A series of other gene products with intriguing putative functions indicate that the minimal pathway established for E. coli [NiFe]-hydrogenase maturation may possess even higher complexity in other organisms.« less

Authors:
; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
944460
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Book
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 59 BASIC BIOLOGICAL SCIENCES; CAPACITY; CYTOPLASM; ENZYMES; ESCHERICHIA COLI; EXPORTS; GENES; HYDROGEN; HYDROGENASES; IRON; MACHINERY; NICKEL; POLYPEPTIDES; PROTEINS; SYNTHESIS; TRANSLOCATION; Hydrogen

Citation Formats

Bock, A., King, P. W., Blokesch, M., and Posewitz, M. C. Maturation of Hydrogenases. United States: N. p., 2006. Web.
Bock, A., King, P. W., Blokesch, M., & Posewitz, M. C. Maturation of Hydrogenases. United States.
Bock, A., King, P. W., Blokesch, M., and Posewitz, M. C. Sun . "Maturation of Hydrogenases". United States. doi:.
@article{osti_944460,
title = {Maturation of Hydrogenases},
author = {Bock, A. and King, P. W. and Blokesch, M. and Posewitz, M. C.},
abstractNote = {Enzymes possessing the capacity to oxidize molecular hydrogen have developed convergently three class of enzymes leading to: [FeFe]-, [NiFe]-, and [FeS]-cluster-free hydrogenases. They differ in the composition and the structure of the active site metal centre and the sequence of the constituent structural polypeptides but they show one unifying feature, namely the existence of CN and/or CO ligands at the active site Fe. Recent developments in the analysis of the maturation of [FeFe]- and [NiFe]- hydrogenases have revealed a remarkably complex pattern of mostly novel biochemical reactions. Maturation of [FeFe]-hydrogenases requires a minimum of three auxiliary proteins, two of which belong to the class of Radical-SAM enzymes and other to the family of GTPases. They are sufficient to generate active enzyme when their genes are co-expressed with the structural genes in a heterologous host, otherwise deficient in [FeFe]-hydrogenase expression. Maturation of the large subunit of [NiFe]-hydrogenases depends on the activity of at least seven core proteins that catalyze the synthesis of the CN ligand, have a function in the coordination of the active site iron, the insertion of nickel and the proteolytic maturation of the large subunit. Whereas this core maturation machinery is sufficient to generate active hydrogenase in the cytoplasm, like that of hydrogenase 3 from Escherichia coli, additional proteins are involved in the export of the ready-assembled heterodimeric enzyme to the periplasm via the twin-arginine translocation system in the case of membrane-bound hydrogenases. A series of other gene products with intriguing putative functions indicate that the minimal pathway established for E. coli [NiFe]-hydrogenase maturation may possess even higher complexity in other organisms.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

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  • Vitrinite reflectance measurements on samples from wells along a line extending for 125 mi (200 km) from the northern shelf area of the Anadarko Basin near the Kansas state line south to the deep part of the basin show that the level of thermal maturity of sedimentary organic matter in the samples was set after maximum burial. Burial history reconstruction curves show the tectonic evolution of this area. Temperatures determined from reflectance values are high as compared to those generally accepted for the onset of hydrocarbon generation and also to those obtained from other similar studies in the basin. Regressionmore » analysis yields a reflectance gradient of 0.109 percent Rm/1,000 ft (300 m) along the profile.« less
  • An investigation was made of the effect of hypophysectomy and growth hormone (GH) replacement regimen (1 mg/100 g twice daily for 30 days); and maturation (from 25 up to 90 days) on the liver and brain glutamine synthetase (GS) mass and turnover rates in rats. The first order decay rate of enzyme /sup 14/C radioactivity was determined between 1 and 4 days to obtain the half-life (T/sub 1/2/) of GS. The hepatic GS mass was determined by immunoassay. GS turnover (GS/sub s/) was calculated from T/sub 1/2/ and the GS mass (i.e., K = 0.693/T/sub 1/2/; GS/sub s/ = Kmore » x GS mass). It was concluded that: (1) GS specific activity is not decreased by hypophysectomy or increased by GH. These results suggested that observed endocrine induced changes in GS are due to changes in GS mass. (2) The liver GS turnover rate is significantly reduced by hypophysectomy and increased by GH replacement. It was proposed that GH specifically enhances synthesis of GS in the liver. (3) Maturation (25, 40, 60, and 90 days) decreases GS turnover rate in both liver and brain of normal rats. This similar effect of maturation suggests that the observed age induced decline in GS turnover rate is not related to GH in all tissues.« less
  • Methanogenesis and growth at both 86 and 90{degree}C were accelerated by pressure up to 750 atm, but growth was not observed above 90{degree}C at 250 atm. However, growth and methanogenesis were uncoupled above 90{degree}C, and the high-temperature limit for methanogenesis was increased by pressure. Substantial methane formation was evident at 98{degree}C and 250 atm, whereas no methane formation was observed at 94{degree}C and 7.8 atm. The present work is the first report on the purification of two hydrogenases, F{sub 420}-reactive and F{sub 420}-nonreactive, from an extremely thermophillic methanogen. The enzymes were purified using anion-exchange chromatography, salt precipitation, and preparative nativemore » PAGE. The major form for both hydrogenases was an aggregate of M{sub r} ca. 510,000. The F{sub 420}-nonreactive enzyme was further resolved into two subunits (M{sub r} 49, 35 K). The pH and temperature optima for the F{sub 420}-nonreactive hydrogenase has no pH optimum for methyl viologen (MV)-reducing activity, and its temperature optimum was 90{degree}C. F{sub 420}-reducing activity, however, was maximal at a pH of 7 and a temperature of 80{degree}C. Both enzymes were active up to about 103{degree}C with MV as an electron acceptor. Each enzyme had a half-life of greater than 3 hours at 70{degree}C. With F{sub 420} as the substrate, the F{sub 420}-active enzyme was less thermostable and lost half its activity in about 70 min at 70{degree}C.« less