Two components of an extracellular protein aggregate of Clostridium thermocellum together degrade crystalline cellulose

Wu, Jiangbin; Orme‐Johnson, William H.; Demain, Arnold L.

doi:10.1021/bi00405a048

Cited by 137 publications

(90 citation statements)

References 35 publications

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“…It was also shown that these scaffolding proteins could bind very tightly to cellulose, whereas the enzymatic subunits did not contain strong CBDs. In partial reconstitution studies, it was demonstrated that SL (CipA) and Ss (CelS) could reassociate to form an active cellulase complex, thus showing that reconstitution between subunits could occur (18). The specific activity of this reconstituted complex was, however, only about 0.4% of that the native enzyme complex.…”

Section: And Discussionmentioning

confidence: 99%

Cellulose promotes extracellular assembly of Clostridium cellulovorans cellulosomes

et al. 1994

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Cellulosome synthesis by Clostridium cellulovorans was investigated by growing the cells in media containing different carbon sources. Supernatant from cells grown with cellobiose contained no cellulosomes and only the free forms of cellulosomal major subunits CbpA, P100, and P70 and the minor subunits with enzymatic activity. Supernatant from cells grown on pebble-milled cellulose and Avicel contained cellulosomes capable of degrading crystalline cellulose. Supernatants from cells grown with cellobiose, pebble-milled cellulose, and Avicel contained about the same amount of carboxymethyl cellulase activity. Although the supernatant from the medium containing cellobiose did not initially contain active cellulosomes, the addition of crystalline cellulose to the cell-free supernatant fraction converted the free major forms to cellulosomes with the ability to degrade crystalline cellulose. The binding of P100 and P70 to crystalline cellulose was dependent on their attachment to the endoglucanase-binding domains of CbpA. These data strongly indicate that crystalline cellulose promotes cellulosome assembly.

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Section: And Discussionmentioning

confidence: 99%

Cellulose promotes extracellular assembly of Clostridium cellulovorans cellulosomes

et al. 1994

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“…This resistance to environmental insults correlates with its resistance to dissociation into individual components even in the presence of urea or nonionic detergent; hence, purification of individual proteins was extremely difficult (174,175). However, we accomplished a breakthrough in the purification of this complex aggregate of cellulolytic proteins (353,354). Using Avicel breakdown as a turbidimetric assay for true cellulase activity and CMC hydrolysis as an assay for endoglucanases, we found the aggregate to contain at least four endoglucanases of different molecular weights accompanying true cellulase activity.…”

Section: Components S L and S Smentioning

confidence: 99%

Cellulase, Clostridia, and Ethanol

Demain

Newcomb

2005

Microbiol Mol Biol Rev

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579

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SUMMARY Biomass conversion to ethanol as a liquid fuel by the thermophilic and anaerobic clostridia offers a potential partial solution to the problem of the world's dependence on petroleum for energy. Coculture of a cellulolytic strain and a saccharolytic strain of Clostridium on agricultural resources, as well as on urban and industrial cellulosic wastes, is a promising approach to an alternate energy source from an economic viewpoint. This review discusses the need for such a process, the cellulases of clostridia, their presence in extracellular complexes or organelles (the cellulosomes), the binding of the cellulosomes to cellulose and to the cell surface, cellulase genetics, regulation of their synthesis, cocultures, ethanol tolerance, and metabolic pathway engineering for maximizing ethanol yield.

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“…degree for his work on gramicidin S biosynthesis, Ph.D. candidate David Wu, in cooperation with Bill Orme-Johnson of the MIT Chemistry Department, isolated the extracellular cellulase and found it to be a multisubunit protein aggregate with a molecular weight of approximately 6.5 × 10 6 . Wu made a major breakthrough when he found that two separate proteins of that complex were required to break down crystalline cellulose: S S , with a molecular weight of 82,000, and S L , with a weight of 250,000 (72). Wu proposed the anchor-enzyme model, in which S L acts as an anchor for S S on the insoluble cellulose surface.…”

Section: Cellulases and Ethanologenic Clostridiamentioning

confidence: 99%

Pickles, Pectin, and Penicillin

Demain

2004

Annu. Rev. Microbiol.

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■ Abstract My professional life has been devoted to the study of microbial products and their biosynthesis, regulation, and overproduction. These have included primary metabolites (glutamic acid, tryptophan, inosinic acid, guanylic acid, vitamin B 12 , riboflavin, pantothenic acid, ethanol, and lactic acid) and secondary metabolites (penicillin, cephalosporins, streptomycin, fosfomycin, gramicidin S, rapamycin, indolmycin, microcin B17, fumagillin, mycotoxins, Monascus pigments, and tetramethylpyrazine). Other areas included microbial nutrition, strain improvement, bioconversions of statins and β-lactams, sporulation and germination, plasmid stability, gel microdroplets, and the production of double-stranded RNA, the polymer xanthan, and enzymes (polygalacturonase, protease, cellulase). Most of the studies were carried out with me by devoted and hardworking industrial scientists for 15 years at Merck & Co. and by similarly characterized students, postdoctorals, and visiting scientists during my 32 years at the Massachusetts Institute of Technology. I owe much of my success to my mentors from academia and industry. My recent research activities with undergraduate students at the Charles A. Dana Research Institute for Scientists Emeriti (R.I.S.E.) at Drew University have been very rewarding and are allowing me to continue my career. CONTENTS

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Two components of an extracellular protein aggregate of Clostridium thermocellum together degrade crystalline cellulose

Cited by 137 publications

References 35 publications

Cellulose promotes extracellular assembly of Clostridium cellulovorans cellulosomes

Cellulose promotes extracellular assembly of Clostridium cellulovorans cellulosomes

Cellulase, Clostridia, and Ethanol

Pickles, Pectin, and Penicillin

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