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A Meinke

Publications and source records attributed to A Meinke.

25 records · Page 2Linked to original sources
PubMed1992

The tertiary structure of endo-beta-1,4-glucanase B (CenB), a multidomain cellulase from the bacterium Cellulomonas fimi.

Endo-beta-1,4-glucanase B (CenB) is a large (110 kDa) extracellular enzyme from the cellulolytic bacterium Cellulomonas fimi. CenB contains five domains, including a typical C.fimi cellulose-binding domain, separated by distinctive linker polypeptides (Meinke et al., 1991b). X-ray scattering analyses show that CenB has a highly elongated shape resembling beads on a string. The sizes of the polypeptides produced by treatment of CenB with proteases, together with their N-terminal amino acid sequences, show that at least two of the four linkers connecting the five domains of CenB are more sensitive to proteolysis than the domains themselves. It is concluded that the beads represent the domains of CenB, the string represents the linkers.

Actinomycetales↗
PubMed1991

Structural and functional relationships in two families of beta-1,4-glycanases.

CenA and Cex are beta-1,4-glycanases produced by the cellulolytic bacterium Cellulomonas fimi. Both enzymes are composed of two domains and contain six Cys residues. Two disulfide bonds were assigned in both enzymes by peptide analysis of the isolated catalytic domains. A further disulfide bond was deduced in both cellulose-binding domains from the absence of free thiols under denaturing conditions. Corresponding Cys residues are conserved in eight of nine other known C. fimi-type cellulose-binding domains. CenA and Cex belong to families B and F, respectively, in the classification of beta-1,4-glucanases and beta-1,4-xylanases based on similarities in catalytic domain primary structure. Disulfide bonds in the CenA catalytic domain correspond to the two disulfide bonds in the catalytic domain of Trichoderma reesei cellobiohydrolase II (family B) which stabilize loops forming the active-site tunnel. Sequence alignment indicates the probable occurrence of disulfides at equivalent positions in the two other family B enzymes. Partial resequencing of the gene encoding Streptomyces KSM-9 beta-1,4-glucanase CasA (family B) revealed five errors in the original nucleotide sequence analysis. The corrected amino acid sequence contains an Asp residue corresponding to the proposed proton donor in hydrolysis catalysed by cellobiohydrolase II. Cys residues which form disulfide bonds in the Cex catalytic domain are conserved in XynZ of Clostridium thermocellum and Xyn of Cryptococcus albidus but not in the other eight known family F enzymes. Like other members of its family, Cex catalyses xylan hydrolysis. The catalytic efficiency (kcat/Km) for hydrolysis of the heterosidic bond of p-nitrophenyl-beta-D-xylobioside is 14,385 min-1.mM-1 at 25 degrees C; the corresponding kcat/Km for p-nitrophenyl-beta-D-cellobioside hydrolysis is 296 min-1.mM-1.

Actinomycetales↗
PubMed1991

Unusual sequence organization in CenB, an inverting endoglucanase from Cellulomonas fimi.

The nucleotide sequence of the cenB gene was determined and used to deduce the amino acid sequence of endoglucanase B (CenB) of Cellulomonas fimi. CenB comprises 1,012 amino acids and has a molecular weight of 105,905. The polypeptide is divided by so-called linker sequences rich in proline and hydroxyamino acids into five domains: a catalytic domain of 607 amino acids at the N terminus, followed by three repeats of 98 amino acids each which are greater than 60% identical, and a C-terminal domain of 101 amino acids which is 50% identical to the cellulose-binding domains of C. fimi cellulases Cex and CenA. A deletion mutant of the cenB gene encodes a polypeptide lacking the C-terminal 333 amino acids of CenB. The truncated polypeptide is catalytically active and, like intact CenB, binds to cellulose, suggesting that CenB has a second cellulose-binding site. The sequence of amino acids 1 to 461 of CenB is 35% identical, with a further 15% similarity, to that of a cellulase from avocado, which places CenB in cellulase family E. CenB releases mostly cellobiose and cellotetraose from cellohexaose. Like CenA, CenB hydrolyzes the beta-1,4-glucosidic bond with inversion of the anomeric configuration. The pH optimum for CenB is 8.5, and that for CenA is 7.5.

Amino Acid Sequence↗
PubMed1991

Multiple domains in endoglucanase B (CenB) from Cellulomonas fimi: functions and relatedness to domains in other polypeptides.

Endoglucanase B (CenB) from the bacterium Cellulomonas fimi is divided into five discrete domains by linker sequences rich in proline and hydroxyamino acids (A. Meinke, C. Braun, N. R. Gilkes, D. G. Kilburn, R. C. Miller, Jr., and R. A. J. Warren, J. Bacteriol. 173:308-314, 1991). The catalytic domain of 608 amino acids is at the N terminus. The sequence of the first 477 amino acids in the catalytic domain is related to the sequences of cellulases in family E, which includes procaryotic and eucaryotic enzymes. The sequence of the last 131 amino acids of the catalytic domain is related to sequences present in a number of cellulases from different families. The catalytic domain alone can bind to cellulose, and this binding is mediated at least in part by the C-terminal 131 amino acids. Deletion of these 131 amino acids reduces but does not eliminate activity. The catalytic domain is followed by three domains which are repeats of a 98-amino-acid sequence. The repeats are approximately 50% identical to two repeats of 95 amino acids in a chitinase from Bacillus circulans which are related to fibronectin type III repeats (T. Watanabe, K. Suzuki, K. Oyanagi, K. Ohnishi, and H. Tanaka, J. Biol. Chem. 265:15659-15665, 1990). The C-terminal domain of 101 amino acids is related to sequences, present in a number of bacterial cellulases and xylanases from different families, which form cellulose-binding domains (CBDs). It functions as a CBD when fused to a heterologous polypeptide. Cells of Escherichia coli expressing the wild-type cenB gene accumulate both native CenB and a stable proteolytic fragment of 41 kDa comprising the three repeats and the C-terminal CBD. The 41-kDa polypeptide binds to cellulose but lacks enzymatic activity.

Amino Acid Sequence↗
PubMed1991

Bacterial cellulose-binding domain-like sequences in eucaryotic polypeptides.

The catalytic domain of endoglucanase II of Trichoderma reesei and the spore germination-specific polypeptide 270-11 of Dictyostelium discoideum contain amino acid sequences which share identity with the sequences of the cellulose-binding domains of several bacterial beta-1,4-glycanases. This is the first report of the presence of such sequences in eucaryotic polypeptides.

Amino Acid Sequence↗
PubMed1990

Nucleotide sequence of the maize chloroplast rpo B/C1/C2 operon: comparison between the derived protein primary structures from various organisms with respect to functional domains.

The genes (rpo B/C1/C2) coding for the beta, beta', beta" subunits of maize (Zea mays) chloroplast RNA polymerase have been located on the plastome and their nucleotide sequences established. The operon is part of a large inversion with respect to the tobacco and spinach chloroplast genomes and is flanked by the genes trnC and rps2. Notable features of the nucleotide sequence are the loss of an intron in rpoC1 and an insertion of approximately 450 bp in rpoC2 compared to the dicotyledons tobacco, spinach and liverwort. The derived amino acid sequence of this additional monocotyledon specific sequence is characterized by acidic heptameric repeat units containing stretches of glutamic acid, tyrosines and leucines with regular spacing. Other structural motifs, such as a nucleotide binding domain in the beta subunit and a zinc finger in the beta' subunit, are compared at the amino acid level throughout the RNA polymerase subunits with the enzymes from other organisms in order to identify functionally important conserved regions.

Amino Acid Sequence↗