Extracellular enzymes of mycobacteria

Abstract Extracellular enzymes were studied in different mycobacteria using a plate substrate assay. All the pathogenic mycobacteria included in the study showed the presence of protease, while lipase, ribonuclease, mucinase and β-lactamase could also be detected in some strains. In contrast, no protease was detected in the 3 saprophytic mycobacteria studied. DNase was not detected in any of the species studied. Thus, the demonstration of extracellular enzymes, in particular of protease, in mycobacteria may be relevant in understanding their role in pathogenicity.     

Solution conformation of d-CTCGAGCTCGAG by two-dimensional NMR: conformational heterogeneity at XhoI cleavage site

Nonexchangeable proton resonances in the 500-MHz NMR spectrum of d-CTCGAGCTCGAG have been assigned by using two-dimensional correlated spectroscopy (COSY) and nuclear Overhauser enhancement spectroscopy (NOESY). 1H-1H coupling constants (J) in the deoxyribose rings have been measured by analyzing intensity and multiplet patterns in the phase-sensitive omega 1-scaled COSY spectra. A modification of the J-resolved technique, called amplitude-modulated J-resolved spectroscopy, has been described and used to increase the accuracy of J measurements. Absorption mode omega 1-scaled NOESY spectra at mixing times in the range 50-200 ms have been analyzed to monitor spin diffusion. A 50-ms spectrum has been used to estimate several interproton distances. The coupling constant and distance data have been used to arrive at sequence-specific sugar geometries and glycosidic torsion angles. The backbone structure has been refined by model building using the FRODO program, employing the sugar geometries and glycosidic torsion angles discussed above. The molecule shows interesting sequence-dependent variations in the structure. The cleavage site of the restriction enzyme XhoI exhibits unique differences in the sugar geometry and backbone torsion angles.     

Isolation and characterization of the hemichrome-stabilized membrane protein aggregates from sickle erythrocytes. Major site of autologous antibody binding

Because the interaction of denatured hemoglobins (i.e. hemichromes) with the red cell membrane has been associated with several abnormalities commonly observed in hemichrome-containing erythrocytes, we have undertaken to isolate and characterize the hemichrome-rich membrane protein aggregates from sickle cells. The aggregates were isolated by two procedures: one at low ionic strength by centrifugation of detergent-solubilized spectrin-depleted inside-out vesicles, and the other at physiological ionic strength by detergent solubilization of whole cells followed by cytoskeletal disruption and centrifugation. The extensively washed aggregates obtained by both methods yielded similar results. These insoluble complexes were found to be highly cross-linked by predominantly intermolecular disulfide bonds; however, other nonreducible covalent linkages were also observed. Both in the presence and absence of reducing agents, the aggregate disintegrated when the hemichromes were removed by high ionic strength, suggesting that the aggregate depended heavily on the cohesive properties of the hemichromes for stability. Protein assays demonstrated that the aggregates comprised approximately 1.3% of the total membrane protein, roughly two-thirds of which appeared to be globin chains. Other major components identified in the aggregate were band 3, ankyrin, bands 4.1, 4.9, and 5, glycophorins A and B, and autologous IgG. Quantitative analysis of the IgG content demonstrated that three-fourths of the surface-bound IgG on washed sickle cells was clustered at these aggregate sites, representing an enrichment of approximately 250-fold over nonaggregated regions of the membrane. Since clustered cell surface IgG is thought to trigger removal of erythrocytes from circulation, the hemichrome-induced membrane reorganization at these aggregate sites may be an important cause of the greatly shortened life span of sickle cells.     

Crystallization and preliminary data of Indian buffalo erythrocyte carbonic anhydrase

The most abundant anhydrase isoenzyme from the erythrocyte of Indian buffalo has been purified using affinity gel and DEAE-cellulose ion-exchange columns and single crystals suitable for X-ray diffraction studies have been obtained. The unit cell dimensions are a = 46.8 A, b = 104.5 A, c = 60.4 A, beta = 91.2 degrees and the space group is P2(1), with two molecules per asymmetric unit.     

Factors related to iron absorption by enzymically isolated leaf cells

The rate of Fe absorption by cells enzymically isolated from tobacco leaves is correlated with the age of the leaves from which the cells are derived. The cells obtained from younger leaves absorb Fe more rapidly than those from older ones. Ca inhibits Fe and Mn absorption. Fe and Mn are mutually antagonistic in their absorption by leaf cells. Ca enhances the inhibition of Mn absorption by Fe, but reduces the inhibition of Fe absorption by Mn. The affinity constant for Fe absorption by leaf cells is low. The chelate EDDHA (ethylenediamine di(o-hydroxyphenylacetate) competitively inhibits Fe absorption.     

Necessity of IgE antibodies and mast cells for manifestation of resistance against larval Haemaphysalis longicornis ticks in mice

Genetically mast cell-deficient WBB6F1-W/Wv mice showed an apparent defect in manifestation of the resistance against larval Haemaphysalis longicornis ticks, but their serum IgE levels increased more than 100-fold after the second tick infestation. Immune sera obtained from the WBB6F1-W/Wv mice were adoptively transferred to the other WBB6F1-W/Wv mice which had received intracutaneous injections of WBB6F1-+/+ mouse-derived cultured mast cells. Because the resistance against ticks was detectable only when both mast cells and IgE antibodies were available, immediate hypersensitivity reaction appeared to have a physiologic role in the manifestation of the resistance against H. longicornis ticks.     

Can fossil fuel energy be recovered and used without any CO2 emissions to the atmosphere?

Reviews in Environmental Science and Bio/Technology - The world’s energy system is still dominated by fossil fuels. While there is a rapid reduction in the cost of renewable energy and the...