Methylation strongly enhances DNA bending in the replication origin region of the Escherichia coli chromosome

Summary Two-dimensional gel electrophoresis, at high and low temperatures, and gel mobilities of circularly permuted DNA segments showed a large bending locus about 50 bp downstream from the right border of the 245 by oriC box, a minimal essential region of autonomous replication on the Escherichia coli chromosome. Bending was strongly enhanced by Dam methylation. In DNA from a Dam^– strain, the mobility anomaly arising from altered conformation was much reduced, but was raised to the original level by methylation in vivo or in vitro. Enhancement of the mobility anomaly was also observed by hybrid formation of the Dam^– strand with the Dam⁺ strand. Near the bending center, GATC, the target of Dam methylase, occurs seven times arranged essentially on the same face of the helix with 10.5 by per turn. We concluded that small bends at each Dam site added up to the large bending detectable by gel electrophoresis.     

The 76 kD cell-adhesion factor from crayfish haemocytes promotes encapsulation in vitro

Summary Semigranular cells from the crayfish, Pacifastacus leniusculus, were separated by Percoll gradient centrifugation and were used to study the encapsulation of foreign particles. The semigranular cells were found strongly to encapsulate glass beads coated with haemocyte lysate in which the prophenoloxidase-activating system had been activated with laminarin or with a low concentration of calcium ions. The granular cells only weakly encapsulated these particles. The encapsulationpromoting factor was purified from haemocyte lysates and found to be a 76 kD protein which was recognized by an antiserum to the previously described 76 kD cell-adhesion factor. After the last step in purification (Con A-Sepharose chromatography), the flowthrough consisted of several proteins, which had some, but less, encapsulation-promoting activity and contained a 30 kD band that was also recognized by the antiserum to the 76 kD cell-adhesion factor. If the haemocyte lysate prepared in low [Ca²⁺] was incubated with a -1,3-glucan prior to purification, no 76 kD protein could be isolated but only a 30 kD protein. The 30 kD protein thus seems to be a degradation product of the 76 kD cell-adhesion factor. We conclude that the 76 kD protein which is released from degranulating haemocytes, and to a lesser extent its 30 kD fragment, can promote encapsulation. Phenoloxidase did not have any encapsulation-promoting activity.     

Effects of vanillin and o-vanillin on induction of DNA-repair networks: modulation of mutagenesis in Escherichia coli

Vanillin and its isomer o-vanillin have an effect on the adaptive and SOS responses, as well as mutagenesis, induced in Escherichia coli by N-methyl-N-nitrosourea (MNU) and UV irradiation, potentiating in some cases and suppressing in others. o-Vanillin markedly inhibited the MNU-induced adaptive response, while both vanillins potentiated the UV-induced SOS response. These phenomena appear to be responsible for the comutagenic or antimutagenic role of these chemicals in MNU and UV mutagenesis.     

Purification and immunological properties of cathepsin B in carpCyprinus carpio

Cathepsin B was purified from the crude extract of carp (Cyprinus carpio) hepato-pancreas by the method involving ammonium sulfate fractionation and five sequential chromatographies monitored the activity with Z-Arg-Arg-MCA as a substrate, and the specific activity increased about 11,400 fold with a 2% recovery. Although the homogeneity of the purified cathepsin B was established on Native-PAGE, it migrated as two bands of 29,000 and 25,000 molecular weights by the single and heavy chains on SDS-PAGE, respectively. The monospecific antibody against the homogeneous cathepsin B was purified by the affinity chromatography on cathepsin B-Sepharose 4B, and did not immunologically react with rat cathepsin B, carp cathepsins H and L but only with carp cathepsin B by immunoelectrophoretic blot analysis. As the result of the tissue and liver distributions of cathepsin B, the remarkable immunological reactivities in the extracts of spleen, kidney and hepato-pancreas in carp and those of pacific cod, yellow fin tuna, skip jack tuna and common mackerel in pisces were detected with the anti-carp hepato-pancreas cathepsin B at molecular weight of nearby 29,000 or 25,000.     

Stimulation of cell division by T4 infection in Escherichia coli dnaEts at nonpermissive temperature.

Summary Filamentous cells resulting from growth of a dnaEts mutant of Escherichia coli at high temperature were stimulated to divide by infection with bacteriophage T4. This effect appears to be related to T4 DNA synthesis; no increase in cell number took place in chloramphenicol-treated, T4-infected cells nor in cells infected with DNA synthesis-less mutants of T4. The ability of cells to divide after T4 infection was dependent on the length of time that the cells had been grown at 42°C, indicating that a potential for cell division accumulates during preincubation.