Plant regeneration from protoplasts of common buckwheat (fagopyrum esculentum)

Protoplasts were isolated from hypocotyls of etiolated seedlings from a diploid and the corresponding autotetraploid variety of common buckwheat (Fagopyrum esculentum). The isolated protoplasts started to divide after 4 days in culture in a modified MS medium. Maximum plating efficiency was approximately 1%. Regenerated calli derived from the tetraploid genotype developed roots easily but were recalcitrant to form shoots. Eighteen months following the initiation of cultures, tetraploid embryoids and shoots emerged after 3 weeks on an MS medium containing 0.1 mg/l gibberellic acid.Abbreviations 2,4-D 2,4 — dichlorophenoxyacetic acid - BAP 6-benzylaminopurine - GA gibberellic acid - MS Murashige and Skoog (1962) medium - NAA 1-naphthaleneacetic acid     

Mechanical precipitation of hemoglobin k?ln.

Hb K?ln (beta 98 Val leads to Met) was found to precipitate rapidly during mechanical shaking. The rate of precipitation of Hb K?ln is 5-6 times faster than that of Hb S. The kinetics of precipitation of the patient's hemolysate, which is a mixture of Hb K?ln and Hb A, showed a biphasic curve indicating that Hb K?ln precipitates independently from Hb A. The instability of Hb K?ln may be attributed to the conformational change in the vicinity of heme. The mechanical shaking may be used as a new method for detection and quantitation of hemoglobin K?ln and other unstable hemoglobins.     

Dissociation, cross-linking, and glycosylation of the coated vesicle proton pump

In order to refine further our structural model of the coated vesicle (H+)-ATPase (Arai, H., Terres, G., Pink, S., and Forgac, M. (1988) J. Biol. Chem. 263, 8796-8802), we have extended our structural analysis to identify peripheral and glycosylated subunits of the pump as well as to identify subunits which are in close proximity in the native (H+)-ATPase complex. Treatment of the purified, reconstituted (H+)-ATPase with 0.30 M KI in the presence or absence of ATP or MgATP results in the release of the 73-, 58-, 40-, 34-, and 33-kDa subunits, leaving behind the 100-, 38-, 19-, and 17-kDa subunits in the membrane. Because the former group of polypeptides is released from the membrane in the absence of detergent, they correspond to peripheral membrane proteins. To determine which subunits are in close proximity, cross-linking of the purified (H+)-ATPase was carried out using the cleavable, bifunctional amino reagent 3,3'-dithiobis(sulfosuccinimidylpropionate) followed by two-dimensional gel electrophoresis. These studies indicate that contact regions exist between the 73- and 58-kDa subunits as well as between the 17-kDa subunit and the 40-, 34-, and 33-kDa subunits. To test for glycosylation of the (H+)-ATPase, the detergent-solubilized complex was treated with neuraminidase followed by electrophoresis and blotting using a peanut lectin/horseradish peroxidase conjugate. Galactose-inhibitable staining of the 100-kDa subunit, together with affinity chromatography of the intact (H+)-ATPase on peanut lectin agarose, indicates that the 100-kDa subunit is glycosylated, most likely at a site exposed on the luminal side of the membrane. These results, together with those presented in the preceding paper (Adachi, I., Arai, H., Pimental, R., and Forgac, M. (1990) J. Biol. Chem. 265, 960-966), were used in the construction of a refined model of the coated vesicle (H+)-ATPase.     

Overexpression of a type II 3-dehydroquinate dehydratase enhances the biotransformation of quinate to 3-dehydroshikimate in Gluconobacter oxydans

Shikimate and 3-dehydroshikimate are useful chemical intermediates for the synthesis of various compounds, including the antiviral drug oseltamivir. Here, we show an almost stoichiometric biotransformation of quinate to 3-dehydroshikimate by an engineered Gluconobacter oxydans strain. Even under pH control, 3-dehydroshikimate was barely detected during the growth of the wild-type G. oxydans strain NBRC3244 on the medium containing quinate, suggesting that the activity of 3-dehydroquinate dehydratase (DHQase) is the rate-limiting step. To identify the gene encoding G. oxydans DHQase, we overexpressed the gox0437 gene from the G. oxydans strain ATCC621H, which is homologous to the aroQ gene for type II DHQase, in Escherichia coli and detected high DHQase activity in cell-free extracts. We identified the aroQ gene in a draft genome sequence of G. oxydans NBRC3244 and constructed G. oxydans NBRC3244 strains harboring plasmids containing aroQ and different types of promoters. All recombinant G. oxydans strains produced a significant amount of 3-dehydroshikimate from quinate, and differences between promoters affected 3-dehydroshikimate production levels with little statistical significance. By using the recombinant NBRC3244 strain harboring aroQ driven by the lac promoter, a sequential pH adjustment for each step of the biotransformation was determined to be crucial because 3-dehydroshikimate production was enhanced. Under optimal conditions with a shift in pH, the strain could efficiently produce a nearly equimolar amount of 3-dehydroshikimate from quinate. In the present study, one of the important steps to convert quinate to shikimate by fermenting G. oxydans cells was investigated.     

Nuclear dynamics of topoisomerase IIβ reflects its catalytic activity that is regulated by binding of RNA to the C-terminal domain

DNA topoisomerase II (topo II) changes DNA topology by cleavage/re-ligation cycle(s) and thus contributes to various nuclear DNA transactions. It is largely unknown how the enzyme is controlled in a nuclear context. Several studies have suggested that its C-terminal domain (CTD), which is dispensable for basal relaxation activity, has some regulatory influence. In this work, we examined the impact of nuclear localization on regulation of activity in nuclei. Specifically, human cells were transfected with wild-type and mutant topo IIβ tagged with EGFP. Activity attenuation experiments and nuclear localization data reveal that the endogenous activity of topo IIβ is correlated with its subnuclear distribution. The enzyme shuttles between an active form in the nucleoplasm and a quiescent form in the nucleolus in a dynamic equilibrium. Mechanistically, the process involves a tethering event with RNA. Isolated RNA inhibits the catalytic activity of topo IIβ in vitro through the interaction with a specific 50-residue region of the CTD (termed the CRD). Taken together, these results suggest that both the subnuclear distribution and activity regulation of topo IIβ are mediated by the interplay between cellular RNA and the CRD.