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Sequence analysis of the Clostridium stercorarium celZ gene encoding a thermoactive cellulase (Avicelase I): Identification of catalytic and cellulose-binding domains (1990)

Jauris, Sigrid ; Rücknagel, Karl P. ; Schwarz, Wolfgang H. ; [et al.]

Springer

Molecular genetics and genomics 223 (1990), S. 258-267

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ISSN: 1617-4623

Keywords: DNA sequence ; Cellulase ; Endoglucanase ; Clostridium stercorarium ; Avocado

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The nucleotide sequence of the celZ gene coding for a thermostable endo-β-1,4-glucanase (Avicelase I) of Clostridium stercorarium was determined. The structural gene consists of an open reading frame of 2958 by which encodes a preprotein of 986 amino acids with an Mr of 109000. The signal peptide cleavage site was identified by comparison with the N-terminal amino acid sequence of Avicelase I purified from C. stercorarium culture supernatants. The recombinant protein expressed in Escherichia coli is proteolytically cleaved into catalytic and cellulose-binding fragments of about 50 kDa each. Sequence comparison revealed that the N-terminal half of Avicelase I is closely related to avocado (Persea americana) cellulase. Homology is also observed with Clostridium thermocellum endoglucanase D and Pseudomonas fuorescens cellulase. The cellulose-binding region was located in the C-terminal half of Avicelase I. It consists of a reiterated domain of 88 amino acids flanked by a repeated sequence about 140 amino acids in length. The C-terminal flanking sequence is highly homologous to the non-catalytic domain of Bacillus subtilis endoglucanase and Caldocellum saccharolyticum endoglucanase B. It is proposed that the enhanced cellulolytic activity of Avicelase I is due to the presence of multiple cellulose-binding sites.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00265062

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Über die Synthese von Tris(trimethylsilyl)silyl-kalium, -rubidium und -caesium und die Molekülstrukturen zweier Toluolsolvate (1993)

Klinkhammer, Karl Wilhelm ; Schwarz, Wolfgang

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 619 (1993), S. 1777-1789

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ISSN: 0044-2313

Keywords: Metal Silyls ; Tris(trimethylsilyl)silyl Potassium ; Tris(trimethylsilyl)silyl Rubidium ; Tris(trimethylsilyl)silyl Cesium ; Alkali Metal Toluene Adducts ; X-ray Structures ; Spectroscopic Data ; Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: About the Synthesis of Tris(trimethylsilyl)silyl Potassium, Rubidium and Cesium and the Molecular Structures of two Toluene Solvates.Solventfree tris(trimethylsilyl)silyl potassium (1), rubidium (2) and cesium (3) are obtained by the reaction of the zink group bis[tris(trimethylsilyl)silyl] derivatives with the appropriate alkali metal in n-pentane. Addition of benzene or toluene to the colourless powders yields deeply coloured solutions. From these solutions single crystals of tris(trimethylsilyl)silyl rubidium - toluene (2/1) (2 a) and tris(trimethylsilyl)silyl cesium - toluene (2/3) (3 a) suitable for X-ray structure analysis are iso- lated [2a: orthorhombic; P212121; a = 1 382.1(3); b = 1 491.7(5); c = 2 106.3(6) pm; Z = 4 (dimers); 3a: orthorhombic; P212121; a = 2 131.0(6); b = 2 833.1(2); c = 925.2(2) pm; Z = 4 (dimers)]. The central structure moieties are folded four-membered Rb2Si2 and Cs2Si2 rings, respectively. Small Si—Si—Si angles (100 to 104°) on the one hand and extreme highfield 29Si-NMR shifts of the central silicon atoms on the other hand indicate a strong charge transfer from the alkali metal atoms to the tris(trimethylsilyl)silyl fragments, i.e. mainly ionic interactions between alkalimetal and silicon atoms.

Notes: Die Umsetzung der Bis[tris(trimethylsilyl)silyl]-Derivate der Zink-Gruppe mit Kalium, Rubidium und Caesium in n-Pentan liefert Tris(trimethylsilyl)silyl-kalium (1), -rubidium (2) und -caesium (3) als farblose, pyrophore Pulver. Nach Zugabe von Benzol order Toluol zu den solvensfreien Verbindungen bilden sich lösliche, farbige Aromaten-Solvate. An den Addukten Tris(trimethylsilyl)silyl-rubidium - Toluol (2/1) (2 a) und Tris(trimethylsilyl)silyl-caesium - Toluol (2/3) (3 a) wurden Kristallstrukturanalysen durchgeführt [2a: orthorhombisch; P212121; a = 1 382,1(3); b = 1 491,7(5); c = 2 106,3(6) pm; Z = 4 (Dimere); 3a: orthorhombisch; P212121; a = 2 131,0(6); b = 2 833,1(2); c = 925,2(2) pm; Z = 4 (Dimere)]. Demzufolge liegen sie im Festkörper als dimere Moleküle mit viergliedrigen, gefalteten Rb2Si2-bzw. Cs2Si2-Ringen vor. Die mit 100 bis 104° relativ kleinen Si—Si—Si-Winkel deuten ebenso wie die im 29Si-NMR-Spektrum beobachtete extreme Tieffeldverschiebung der Resonanzen des zentralen Siliciumatoms auf eine weitgehende Ladungsübertragung von den Alkalimetallatomen auf das Tris(trimethylsilyl)silyl-Fragment, d. h. vorwiegend ionische Wechselwirkungen in den Ringen aus Alkalimetall- und Siliciumatomen hin.

Additional Material: 5 Ill.