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Title: | Formylmethanofuran formation in Methanobacterium thermoautotrophicum |
Author(s): | Bobik, Thomas Aquinas |
Doctoral Committee Chair(s): | Wolfe, R.S. |
Department / Program: | Microbiology |
Discipline: | Microbiology |
Degree Granting Institution: | University of Illinois at Urbana-Champaign |
Degree: | Ph.D. |
Genre: | Dissertation |
Subject(s): | Biology, Microbiology |
Abstract: | The initial step of methanogenesis from CO$\sb2$ is the formation of formyl-methanofuran (formyl-MFR) from methanofuran, CO$\sb2$ and H$\sb2$. This reaction is not measurable in vitro unless activated. The enzymology, and the activation of this reaction were studied. It was found that the heterodisulfide of 2-mercaptoethanesulfonic acid and N-(7-mercaptoheptanoyl)threonine-O$\sp3$-phosphate (CoM-S-S-HTP) was directly involved in the activation of formyl-MFR formation. Preliminary evidence indicated that CoM-S-S-HTP activated electron transfer to formyl-MFR formation; CoM-S-S-HTP was found to activate an unknown electron carrier present in cell extracts of Methanobacterium, and the low potential reducing agent titanium-(III)$\cdot$citrate was found to bypass the CoM-S-S-HTP requirement of formyl-MFR synthesis. Additionally, CoM-S-S-HTP was shown to be a product of the methyl-reductase and the fumarate reductase reactions, and evidence indicated that each of these reactions activated formyl-MFR formation. Moreover, CoM-S-S-HTP was shown to be reduced by a heterodisulfide reductase and this reduction inactivated formyl-MFR formation. Fractionation procedures were employed to resolve cell extract into two components each of which was required for formyl-MFR formation. One fraction (in the presence of CoM-S-S-HTP) reduced the redox dye metronidazole with electrons from H$\sb2$, and the other fraction contained formyl-MFR dehydrogenase activity. Neither ATP nor a membrane fraction was required to reconstitute formyl-MFR formation, and the non-deazaflavin reducing hydrogenase was sufficient for formyl-MFR formation. It was proposed that the activation of formyl-MFR formation was used to coordinate the rate of CO$\sb2$ fixation with the rates of methanogenesis and cell carbon synthesis. |
Issue Date: | 1990 |
Type: | Text |
Language: | English |
URI: | http://hdl.handle.net/2142/22839 |
Rights Information: | Copyright 1990 Bobik, Thomas Aquinas |
Date Available in IDEALS: | 2011-05-07 |
Identifier in Online Catalog: | AAI9021651 |
OCLC Identifier: | (UMI)AAI9021651 |
This item appears in the following Collection(s)
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Dissertations and Theses - Microbiology
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Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois