Oxidative deamination of epsilon-aminolysine residues and formation of Schiff base cross-linkages in cell envelopes of Escherichia coli

Morphological and physiological changes induced by high hydrostatic pressure in exponential- and stationary-phase cells of Escherichia coli: relationship with cell death

The relationship between a loss of viability and several morphological and physiological changes was examined with Escherichia coli strain J1 subjected to high-pressure treatment. The pressure resistance of stationary-phase cells was much higher than that of exponential-phase cells, but in both types of cell, aggregation of cytoplasmic proteins and condensation of the nucleoid occurred after treatment at 200 MPa for 8 min. Although gross changes were detected in these cellular structures, they were not related to cell death, at least for stationary-phase cells. In addition to these events, exponential-phase cells showed changes in their cell envelopes that were not seen for stationary-phase cells, namely physical perturbations of the cell envelope structure, a loss of osmotic responsiveness, and a loss of protein and RNA to the extracellular medium. Based on these observations, we propose that exponential-phase cells are inactivated under high pressure by irreversible damage to the cell membrane. In contrast, stationary-phase cells have a cytoplasmic membrane that is robust enough to withstand pressurization up to very intense treatments. The retention of an intact membrane appears to allow the stationary-phase cell to repair gross changes in other cellular structures and to remain viable at pressures that are lethal to exponential-phase cells.

Histone H1 is a substrate for lysyl oxidase and contains endogenous sodium borotritide-reducible residues

Incubation of purified bovine aortic lysyl oxidase with rat liver or calf thymus H1 histone results in the catalytic formation of hydrogen peroxide, indicating the substrate potential of H1 for this connective tissue enzyme. Sodium borotritide-reducible residues consistent with aminoadipic semialdehyde and the lysinonorleucine crosslinkage were generated in H1 by incubation with lysyl oxidase. H1 histone also contains endogenous reducible functions including an unidentified prominent tritiated peak eluting near tyrosine as well as other lesser peaks, one of which is consistent with lysinonorleucine.

The microfibrillar components of porcine lung elastic fiber

Lung elastic fiber was isolated from anatomically defined porcine parenchymal tissue. Constituent microfibrillar acidic structural glycoproteins (external and meso) were obtained by mild dissociative quantitative procedures, leaving the elastin-rich fraction as the insoluble residue. The presumptive cross-link lysylnorleucine was identified in both of the highly aggregated acidic structural glycoprotein fractions. The external-acidic structural glycoproteins require dithiothreitol but not sodium dodecyl sulfate for solubility. Both sodium dodecyl sulfate and dithiothreitol at 55 degrees C are required to release meso-acidic structural glycoproteins from the elastic fiber. On the basis of physical characteristics, I propose a new fraction from elastic fiber, the meso-acidic structural glycoprotein. The meso-acidic structural glycoproteins may have been in longest and closest contact with the elastin core of the elastic fiber. Alkali-soluble peptides from the elastin-rich fraction contained desmosine and high concentrations of hydroxyproline, polar amino acids and lysylnorleucine. The cross-link, lysylnorleucine, may be evidence of covalent bonding of glycoprotein to elastin, explaining my inability to obtain the biopolymer elastin with the composition of tropoelastin corrected for the desmosine-lysine content.