Properties of exgS, a gene for a major subunit of the Clostridium cellulovorans cellulosome

Liu, Chichi; Doi, Roy H.

doi:10.1016/s0378-1119(98)00081-x

Cited by 58 publications

(53 citation statements)

References 37 publications

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“…To identify these proteins, their amino termini were sequenced. The sequences of the 180-, 110-, and 75-kDa polypeptides were identical to those of the major cellulosomal subunits, i.e., scaffolding protein CbpA (ATSSMSV) (26), endoglucanase EngE (AEAN XTTKG) (31), and exoglucanase ExgS (APVVPNN) (20), respectively. On the other hand, the polypeptides in the noncellulosomal fraction ranged from 25 to 130 kDa (Fig.…”

Section: Resultsmentioning

confidence: 95%

“…Clostridium cellulovorans (ATCC 35296) (28), an anaerobic, mesophilic, and spore-forming bacterium, produces a large extracellular polysaccharolytic multicomponent complex (with a molecular weight of about one million) called the cellulosome (7), in which several cellulases are tightly bound to a scaffolding protein called CbpA (26). The C. cellulovorans cellulosome consists of three major subunits-CbpA, P100, and P70-and several minor subunits (20,27,31). Recent work in our laboratory has contributed to better understanding of the molecular biology of degradation of crystalline cellulose by C. cellulovorans cellulosome (7,8,33).…”

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confidence: 99%

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Characterization of Xylanolytic Enzymes in Clostridium cellulovorans : Expression of Xylanase Activity Dependent on Growth Substrates

2001

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Xylanase activity of Clostridium cellulovorans, an anaerobic, mesophilic, cellulolytic bacterium, was characterized. Most of the activity was secreted into the growth medium when the bacterium was grown on xylan. Furthermore, when the extracellular material was separated into cellulosomal and noncellulosomal fractions, the activity was present in both fractions. Each of these fractions contained at least two major and three minor xylanase activities. In both fractions, the pattern of xylan hydrolysis products was almost identical based on thin-layer chromatography analysis. The major xylanase activities in both fractions were associated with proteins with molecular weights of about 57,000 and 47,000 according to zymogram analyses, and the minor xylanases had molecular weights ranging from 45,000 to 28,000. High ␣-arabinofuranosidase activity was detected exclusively in the noncellulosomal fraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that cellulosomes derived from xylan-, cellobiose-, and cellulose-grown cultures had different subunit compositions. Also, when xylanase activity in the cellulosomes from the xylan-grown cultures was compared with that of cellobiose-and cellulose-grown cultures, the two major xylanases were dramatically increased in the presence of xylan. These results strongly indicated that C. cellulovorans is able to regulate the expression of xylanase activity and to vary the cellulosome composition depending on the growth substrate.Plant cell walls, the major reservoir of fixed carbon in nature, have three major polymers: cellulose, hemicellulose, and lignin (29). In anaerobic environments and decaying plant materials, complex communities of interacting microorganisms carry out the decomposition of lignocellulose. Among the lignocellulolytic bacteria, cellulolytic clostridia play important roles in plant biomass turnover (19). Clostridium cellulovorans (ATCC 35296) (28), an anaerobic, mesophilic, and spore-forming bacterium, produces a large extracellular polysaccharolytic multicomponent complex (with a molecular weight of about one million) called the cellulosome (7), in which several cellulases are tightly bound to a scaffolding protein called CbpA (26). The C. cellulovorans cellulosome consists of three major subunits-CbpA, P100, and P70-and several minor subunits (20,27,31). Recent work in our laboratory has contributed to better understanding of the molecular biology of degradation of crystalline cellulose by C. cellulovorans cellulosome (7,8,33). Furthermore, we have also found that C. cellulovorans utilizes not only cellulose but also xylan, pectin, and several other carbon sources (28, 32). Among these carbon sources, xylan is mainly found in secondary walls of plants, the major component of woody tissue (35) and, after cellulose, xylan is the most abundant renewable polysaccharide in plants (34).Xylan, which has a backbone of ␤-1,4-linked xylopyranosyl residues contains various substituted side-groups such as acetyl, L-arabinofuranosyl, and o-met...

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Section: Resultsmentioning

confidence: 95%

mentioning

confidence: 99%

Characterization of Xylanolytic Enzymes in Clostridium cellulovorans : Expression of Xylanase Activity Dependent on Growth Substrates

2001

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“…However, the composition of the major subunits CbpA (Shoseyov et al, 1992), EngE (Tamaru & Doi, 1999) and ExgS (Liu & Doi, 1998) was relatively constant for all the subpopulations. The cellulosomal fractions which showed higher cellulase activity contained CbpA, EngE/EngK, ExgS/EngH and EngL (Liu & Doi, 1998;Shoseyov & Doi, 1990;Shoseyov et al, 1992;Tamaru & Doi, 1999. All these enzymes are encoded in the large cbpA gene cluster cbpA-exgS-engHengK-hbpA-engL , except for EngE.…”

Section: Discussionmentioning

confidence: 96%

Effect of carbon source on the cellulosomal subpopulations of Clostridium cellulovorans

et al. 2005

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Clostridium cellulovorans produces a cellulase enzyme complex called the cellulosome. When cells were grown on different carbon substrates such as Avicel, pectin, xylan, or a mixture of all three, the subunit composition of the cellulosomal subpopulations and their enzymic activities varied significantly. Fractionation of the cellulosomes (7-11 fractions) indicated that the cellulosome population was heterogeneous, although the composition of the scaffolding protein CbpA, endoglucanase EngE and cellobiohydrolase ExgS was relatively constant. One of the cellulosomal fractions with the greatest endoglucanase activity also showed the highest or second highest cellulase activity under all growth conditions tested. The cellulosomal fractions produced from cells grown on a mixture of carbon substrates showed the greatest cellulase activity and contained CbpA, EngE/EngK, ExgS/EngH and EngL. High xylanase activity in cellulose, pectin and mixed carbon-grown cells was detected with a specific cellulosomal fraction which had relatively larger amounts of XynB, XynA and unknown proteins (35-45 kDa). These results in toto indicate that the assembly of cellulosomes occurs in a non-random fashion.

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“…However, in some family 9 cellulases, their respective catalytic domains are immediately adjacent to a family IIIc CBD, of which many aromatic amino acid residues on the planar strip thought to be crucial for binding to cellulose are not conserved (19). Examples include CelI (101,123,373), CelN (373), CelQ (9), CelF of C. thermocellum (19), CelG of C. cellulolyticum (90), EngH of C. cellulovorans (194,321), CelZ of C. stercorarium (134), and cellulase E4 of Thermomonospora fusca (132). Family IIIc CBDs are considered to play a very different role from that of the family IIIa CBDs.…”

Section: Cellulose-binding Domainmentioning

confidence: 99%

Cellulase, Clostridia, and Ethanol

Demain

Newcomb

2005

Microbiol Mol Biol Rev

804

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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Properties of exgS, a gene for a major subunit of the Clostridium cellulovorans cellulosome

Cited by 58 publications

References 37 publications

Characterization of Xylanolytic Enzymes in Clostridium cellulovorans : Expression of Xylanase Activity Dependent on Growth Substrates

Characterization of Xylanolytic Enzymes in Clostridium cellulovorans : Expression of Xylanase Activity Dependent on Growth Substrates

Effect of carbon source on the cellulosomal subpopulations of Clostridium cellulovorans

Cellulase, Clostridia, and Ethanol

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