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PubMed1995

Comparative biology of the neuronal ceroid-lipofuscinoses (NCL): an overview.

Multiple forms of ceroid-lipofuscinosis occur in human beings and animals. They are characterized by brain and retinal atrophy associated with selective necrosis of neurons. This neurodegenerative disease appears associated with the disease process rather than storage of fluorescent lipopigment per se, and there is now growing evidence that pathogenesis may involve mitochondria rather than a primary defect of lysosomal catabolism. Of the forms of ceroid-lipofuscinosis studied, most but not all reflect accumulation of subunit c of mitochondrial ATP synthase. If there is a common denominator between all forms other than the presence of fluorescent lipopigment, then it may be the accumulation of hydrophobic protein. Analogous diseases in animals can be expected to reflect the same spectrum of biochemical changes, and they warrant in-depth study to help understand the pathogenesis and heterogeneity of the group.

Animals↗
PubMed1998

Catalytic thiol and carboxylate: role of cysteine and glutamic acid in the xylosidic activity of endoxylanase from Chainia sp. (NCL 82-5-1).

Chemical modification of the endoxylanase from Chainia sp. with group-specific chemical modifiers in the absence and presence of substrate and kinetics of modification revealed the involvement of a thiol and a carboxylate in the catalytic function of the enzyme. The active-site peptides were chemically labeled and sequenced. The sequence alignment of the chemically labeled peptide with other family G/11 xylanases showed that the catalytic glutamate of Chainia xylanase is located in a highly homologous region and may function as an acid/base catalyst while thiol of the Cys may function as a nucleophile.

Amino Acid Sequence↗
PubMed1999

Ultrastructural and electrophysiological correlation of the genotypes of NCL.

Several genetically different, but clinically similar childhood forms of neuronal ceroid lipofuscinosis are now recognized. Accurate diagnosis is important so that appropriate genetic advice can be given, molecular analysis can be undertaken, and prenatal testing can be considered. A combined clinical, electrophysiological, and histological (light and electron microscopy) approach offers the most reliable means of diagnosis in the majority of patients. Patients with an unusual presentation will also be identified.

Electroencephalography↗
PubMed1999

A murine model for juvenile NCL: gene targeting of mouse Cln3.

JNCL is a neurodegenerative disease of childhood caused by mutations in the CLN3 gene. A mouse model for JNCL was created by disrupting exons 1-6 of Cln3, resulting in a null allele. Cln3 null mice appear clinically normal at 5 months of age; however, like JNCL patients, they exhibit intracellular accumulation of autofluorescent material. A second approach will generate mice in which exons 7 and 8 of Cln3 are deleted, mimicking the common mutation in JNCL patients.

Animals↗
PubMed1992

Presence of an essential lysine residue in a GDP-fucose protected site of the alpha 1----3fucosyltransferase from human small cell lung carcinoma NCl-H69 cells.

The NCI-H69 cell alpha 1----3fucosyltransferase has been purified from a 0.2% Triton X-100R solubilized enzyme fraction by GDP-hexanolamine-Sepharose affinity chromatography and Superose 12 gel filtration. Photoaffinity labeling experiments with 125I-GDP-hexanolaminyl-4-azidosalicylic acid present in concentrations equivalent to 0.5 and 1 times Ki of the inhibitor for the enzyme indicated that labeling of the 45-kDa protein band could be inhibited by addition of 400 microM GDP-fucose but was not effected by similar concentrations of either GDP-mannose or GDP-glucose. The purified enzyme was applied to studies intended to define catalytically essential amino acid residues of the protein. Incubation of the enzyme in the presence of increasing concentrations of pyridoxal 5'-phosphate was found to result in irreversible inactivation of the enzyme after NaBH4 reduction. The donor substrate, GDP-fucose, was found to protect the enzyme from inactivation. Little or no protection was found for either GDP-mannose or the acceptor substrate nLc4. Pyridoxal 5'-phosphate was shown to behave as a competitive inhibitor with respect to GDP-fucose with a Ki of 105 microM. Labeling with 3H-pyridoxal 5'-phosphate resulted in the incorporation of approximately 8 mol pyridoxal 5'-phosphate per mole subunit. Parallel experiments containing GDP-fucose indicated protection of one site per subunit correlated with GDP-fucose binding. Acid hydrolysis and chromatographic analysis of the 3H-pyridoxylated protein indicated greater than 95% of the 3H label was recovered as pyridoxyl-lysine irrespective of whether GDP-fucose was present or not during labeling. These studies indicate the presence of a catalytically essential lysine residue associated with GDP-fucose binding to this enzyme. This information will be of value in further studies of this and other alpha 1----3fucosyltransferases and may suggest a practical basis for modulation of enzyme activity in the cell.

Binding Sites↗
PubMed1999

NCL-CD10-270: a new monoclonal antibody recognizing CD10 in paraffin-embedded tissue.

CD10 (CALLA) antigen is expressed in a wide variety of epithelial and nonepithelial tissues, but its most significant application is in the diagnosis and classification of certain types of malignant lymphoma and leukemia. CD10 is expressed in a high percentage of cases of acute lymphoblastic leukemia (ALL), follicular lymphoma, Burkitt's lymphoma, and some hematopoietic tumors. Although the antigen is not lineage specific, CD10 expression is widely used to define subgroups within B-ALL and is a useful tool for detecting the presence of leukemic blasts in the bloodstream. Currently available monoclonal antibodies to CD10 have been found to be effective only in fresh-frozen tissue and for techniques such as flow cytometry. We have used a recombinant protein corresponding to the whole of CD10 to generate a monoclonal antibody that is effective in paraffin-embedded tissue sections. We have used this antibody to assay for the presence of CD10 on a range of normal and pathological tissues. Strong staining was seen in lymphoid germinal centers, renal tubules, glomeruli, syncytiotrophoblast, hepatic parenchymal canaliculi, B-lineage ALL, follicle center cell lymphoma, and a proportion of cases of large-B-cell lymphoma. We believe that this antibody will be of value in the characterization of malignant lymphoma, in particular the differential diagnosis of small-B-cell lymphoma and subtyping of lymphoblastic leukemia, as well as the investigation of the significance of expression of CD10 in other normal and pathological tissues.

Animals↗
PubMed1998

Thermodynamics of ligand (substrate/end product) binding to endoxylanase from Chainia sp. (NCL-82-5-1): isothermal calorimetry and fluorescence titration studies.

The binding of xylo-oligosaccharides to Chainia endoxylanase resulted in a decrease in fluorescence intensity of the enzyme with the formation of 1:1 complex. Equilibrium and thermodynamic parameters of ligand binding were determined by fluorescence titrations and titration calorimetry. The affinity of xylanase for the oligosaccharides increases in the order X2<X3<X4</=X5. Contributions from the enthalpy towards the free energy change decreased with increasing chain length from X2 to X4, whereas an increase in entropy was observed, the change in enthalpy and entropy of binding being compensatory. The entropically driven binding process suggested that hydrophobic interactions as well as hydrogen bonds play a predominant role in ligand binding.

Actinomycetales↗
PubMed2004

Paramagnetic precursors for supramolecular assemblies: selective syntheses, crystal structures, and electrochemical and magnetic properties of Ru2(O2CMe)4-n(formamidinate)nCl complexes, n = 1-4.

Reactions of Ru(2)(O(2)CMe)(4)Cl with two formamidines, HDXyl(2,6)F = N,N'-di(2,6-xylyl)formamidine and HDAniF = N,N'-di(p-anisyl)formamidine, have been investigated with the idea of synthesizing compounds with a mixed set of ligands having different labilities to be used as precursors of paramagnetic, higher-order assemblies. Depending on the formamidine and the reaction conditions, several Ru(2)(5+) compounds of the type Ru(2)(O(2)CMe)(4)(-)(n)(DArF)(n)Cl (DArF = anion of an N,N'-diarylformamidine) have been isolated. With the bulky formamidine HXyl(2,6)F, the compounds Ru(2)(O(2)CMe)(3)(DXyl(2,6)F)Cl (1) and trans-Ru(2)(O(2)CMe)(2)(DXyl(2,6)F)(2)Cl (2) were obtained. From reactions with appropriate amounts of HDAniF in THF and in the presence of NEt(3) and LiCl, complexes of the general type Ru(2)(O(2)CMe)(4)(-)(n)(DArF)(n)Cl (n = 1-4) were selectively obtained. For n = 2, only the cis isomer was obtained. The choice of solvent in reactions of Ru(2)(O(2)CMe)(4)Cl and HDAniF is of great importance. Toluene favored the formation of the fully substituted Ru(2)(5+) complex Ru(2)(DAniF)(4)Cl (3), whereas MeOH resulted in a disproportionation reaction that gave the edge-sharing bioctahedral Ru(3+)Ru(3+) complex [trans-Ru(2)(mu-OMe)(2)(mu-O(2)CMe)(2)(HDAniF)(4)]Cl(2) (6) and the Ru(2)(4+) complex Ru(2)(DAniF)(4) (7). Complexes 6 and 7 with an Ru(2)(6+) and Ru(2)(4+) core, respectively, are diamagnetic, whereas all Ru(2)(5+) complexes are paramagnetic with sigma(2)pi(4)delta(2)(pi*delta*)(3) ground-state electronic configurations and large zero-field splitting contributions. All compounds show rich and complex electrochemical behavior.

Journal Article↗
PubMed1996

Structural environment of an essential cysteine residue of xylanase from Chainia sp. (NCL 82.5.1).

N-(2,4-Dinitroanilino)maleimide (DAM) reacts covalently with the thiol group of the xylanase from Chainia leading to complete inactivation in a manner similar to N-ethylmaleimide, but provides a reporter group at the active site of the enzyme. Increasing amounts of xylan offered enhanced protection against inactivation of the xylanase by DAM. Xylan (5 mg) showed complete protection, providing evidence for the presence of cysteine at the substrate-binding site of the enzyme. Kinetics of chemical modification of the xylanase by DAM indicated the involvement of 1 mol of cysteine residue per mol of enzyme, as reported earlier [Deshpande, Hinge and Rao (1990) Biochim. Biophys. Acta 1041, 172-177]. The second-order rate constant for the reaction of DAM with the enzyme was 3.61 x 10(3) M-1.min-1. The purified xylanase was alkylated with DAM and digested with pepsin. The peptides were separated by gel filtration. The specific modified cysteinyl peptide was further purified by reverse-phase HPLC. The active-site peptide was located visually by its predominant yellow colour and characterized by a higher A340 to A210 ratio. The modified active-site peptide has the sequence: Glu-Thr-Phe-Xaa-Asp. The sequence of the peptide was distinctly different from that of cysteinyl peptide derived from a xylanase from a thermotolerant Streptomyces species, but showed the presence of a conserved aspartic acid residue consistent with the catalytic regions of other glucanases.

Actinomycetales↗
PubMed2002

Characterization of alkaline thermoactive cellulase-free xylanases from alkalophilic Bacillus (NCL 87-6-10).

Two alkaline xylanases designated as "A" and "C", respectively, were isolated from the culture filtrates of the alkalophilic Bacillus grown on a wheat bran-yeast extract medium. The two xylanases occurred in the culture filtrate in a ratio of 10:90. These xylanases were purified to homogeneity on a CM-Sephadex matrix followed by further separation of Xylanase "A" on a phenyl sepharose column and preparative electrophoresis. The two xylanases differed considerably in their physico-chemical properties, kinetics and in their mode of action. Xylanase "C" had a molecular weight of 25,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis and was a cationic protein with a pI of 8.9. In contrast xylanase "A" had a molecular weight of 45,000 with a pI of 5.3. The two xylanases showed distinct differences in their hydrolysis pattern. Xylanase "A" produced comparatively larger amounts of small molecular weight oligosaccharides and xylose namely xylotriose (X(3)), xylobiose (X(2)) and xylose even in the initial stages of hydrolysis (2 and 5 h) while xylanase "C" produced negligible amounts of X(2) and no xylose for the same period of incubation. At 24 h only traces of xylose was produced by xylanase "C" while substantial amounts of the monomer was produced by xylanase A in 24 h. Xylanase "A" had a broad pH optimum ranging from pH 6.0-10.0 at 40-60 degrees C while xylanase "C" had an optimum pH of 8.0 at 40-60 degrees C. Xylanases "A" and "C" differed in their K(m) and V(max) values. Xylanase "A" had a K(m) of 1.67 mg/ml and a V(max) of 3.85 x 10(2) micromol/ml/min, whereas xylanase "C" had a K(m) of 10 mg/ml and a V(max) of 1.43 x 10(4) micromol/ml/min.

Bacillus↗