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Some peculiarities of functioning of H+-ATPase from the membranes of the anaerobic bacterium Lactobacillus casei.

Radiation inactivation analysis gave the target sizes of 176 +/- 5 kDa and 275 +/- 33 kDa for ATPase from anaerobic Lactobacillus casei and aerobic Micrococcus luteus bacteria respectively. The values are close to the known molecular masses of the enzymes. Thus, to function the L. casei ATPase, like the F1-ATPases, requires a complete structure composed of all the enzyme subunits. L. casei ATPase is inhibited by 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole owing to modification of an amino acid residue(s) with pK greater than 8.5. L. casei ATPase consists of six identical subunits and differs from alpha 3 beta 3 gamma delta epsilon-type F1-ATPases in a number of catalytic properties. Namely, ATP hydrolysis under the 'unisite' conditions proceeds at a relatively high rate suggesting the absence of cooperative interactions between the catalytic sites. Contrary to mitochondrial F1-ATPase. L. casei ATPase does not form an inactive complex with ADP. These findings imply essential differences in the operating mechanism for L. casei ATPase and F1 ATPase.

Azides↗

[The antitumor activity of Lactobacillus casei--the direct effects of L. casei to human tumor cell lines].

The effects of somatic components of Lactobacillus casei (L. casei) were studied on cell growth in vitro. L. casei was able to suppress the growth of MT-2, MT-4 cells from adult T-cell leukemia, Molt-4 cells from acute lymphoblastic leukemia and U-937 cells from promonocytic leukemia. This effect was obviously different from the cytotoxicity of Vinbrastin, an anti-cancer drug. Flow cytometric experiments employing BrdU-anti BrdU antibody demonstrated an increase of cells in G1 + G0 phases (pre-DNA synthesis phases) by the treatment of L. casei, therefore L. casei maybe acts as a low grade inhibitor of the protein synthesis. PC-treated L. casei had no more inhibition on cell growth than the non-treated one.

Cell Cycle↗

Dihydrofolate reductase inhibition. A study in the use of X-ray crystallography, molecular graphics, and quantitative structure-activity relations in drug design.

Substituent constants and regression analyses are used to formulate quantitative structure-activity relationships (QSAR) for the inhibition by 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-(3-X-phenyl)-s-triazines of purified dihydrofolate reductase (DHFR) from L. Casei cells, bovine liver, and murine leukemia cells (L5178Y). The QSAR for the activity of the triazines on purified DHFR is compared with the QSAR for their action on L. casei cell culture and murine L5178Y cell culture. The QSAR for action on purified DHFR is similar to that on wild type cells; however, the QSAR for these cells differs remarkably from QSAR for both types of cells that are resistant to methotrexate (MTX). The conclusion from these analyses is that cells resistant to MTX protect themselves from this highly hydrophilic drug by developing a hydrophobic barrier. Our understanding of DHFR interaction with drugs is rapidly increasing via QSAR, and X-ray crystallography, combined with the new molecular graphics of Langridge's group, promises to expedite the process. The value of three-dimensional color graphics is discussed, with the aid of color stereo views of L. casei and E. coli DHFR.

Animals↗

The effect of substrate analogs on the circular dichroic spectra of thymidylate synthetase from Lactobacillus casei.

Circular dichroism studies from 290 to 400 nm with the thymidylate synthetase from Lactobacillus casei revealed characteristic Cotton effects in the presence of various folate analogs plus 5-fluoro-2'-deoxyuridylate. Omission of either substrate analog prevented the appearance of the Cotton effects. When 5-fluoro-2'-deoxyuridylate and (+/-)-5,10-methylenetetrahydrofolate are mixed with the synthetase, a ternary complex results which yields distinctive minor negative ellipicity bands at 285 and 332 nm and a major negative ellipticity bands at 285 and 332 nm and a major positive band at 305 nm. Similar results were obtained with the ternary complex containing (+)-5,10-methylenetetrahydrofolate, but the enzymically inactive (-) diastereoisomer induced only the positive band at 305 nm. More intense Cotton effects were elicited by (+/-)-5,11-methylenetetrahydrohomofolate with a major positive ellipticity band at 308 nm and a minor negative band at 335 nm. A ternary complex was also formed with dihydrofolate, which provided a major circular dichroic band at 305 nm and a broad minor negative band in the region of 335 nm. Deoxyuridylate and thymidylate also formed ternary complexes with dihydrofolate, but their ellipicity bands were much less intense. Other folate analogs that formed ternary complexes with 5-fluoro-2'-deoxyuridylate to provide characteristic circular dichroic spectra were tetrahydrofolate, tetrahydrohomofolate, 10-methyltetrahydrofolate, and a 2-amino-4-hydroxyquinazoline derivative. By measuring the increment in ellipticity at 305 nm on addition of specific ligands to enzyme solutions, it was determined that the L. casei thymidylate synthetase contains two binding sites for 5-fluoro-2'-deoxyuridylate and for each of the diastereoisomers of 5,10-methylenetetrahydrofolate. An improved procedure is presented for the large-scale purification and crystallization of L. casei thymidylate synthetase.

Binding Sites↗

Use of polymerase chain reaction techniques and sodium dodecyl sulfate-polyacrylamide gel electrophoresis for differentiation of oral Lactobacillus species.

BACKGROUND/AIMS: The genus Lactobacillus has been associated with dental caries in humans, although it is seldom speciated due to lack of simple and nonlaborious identification methods. A considerable heterogeneity among Lactobacillus species has been demonstrated. The purpose of this study was to develop simple methods combining restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified 16S rRNA (16S rRNA gene PCR-RFLP) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for the identification of 13 reference strains of Lactobacillus. METHODS: The 16S rRNA gene sequences were amplified by PCR using universal primers and digestion of PCR products with the restriction endonucleases, HpaII and HaeIII. The 16S rRNA gene PCR-RFLP is reproducible and has been proved to be useful for differentiating Lactobacillus strains to species level. Seventy-seven Lactobacillus isolates from a Thai population were used to show the applicability of the identification test. RESULTS: PCR-RFLP alone had limitations, because the RFLP patterns of Lactobacillus casei and Lactobacillus rhamnosus and of Lactobacillus acidophilus and Lactobacillus crispatus showed similar patterns; however, these could be differentiated by SDS-PAGE. Of the 77 isolates, 38 were identified as Lactobacillus fermentum, 25 as L. rhamnosus, 5 as Lactobacillus salivarius, 5 as L. casei, 3 as L. acidophilus and 1 as Lactobacillus plantarum. CONCLUSION: 16S rRNA gene PCR-RFLP, using HpaII and HaeIII, together with SDS-PAGE protein profiles could be an alternative method for the identification of oral Lactobacillus strains to species level, and may be applicable for large-scale studies on the association of Lactobacillus to dental caries.

Adult↗

Continuous-flow automation of the Lactobacillus casei serum folate assay.

A method is described for the continuous-flow automation of the serum folate assay using Lactobacillus casei. The total incubation period is approximately four hours. The growth response of the organism to folate is estimated by measuring the rate of reduction of 2,3,5-triphenyl tetrazolium chloride (TTC). A simple continuous culture apparatus is used to grow the inoculum. Supplementation of the assay medium is necessary to obtain parallel results. A statistical assessment shows a favourable comparison with the whole-serum tube assay using a chloramphenicol resistant strain of L. casei. The method is less sensitive to inhibitory substances than the tube assay.

Autoanalysis↗

Applications of probiotics.

Although not all action mechanisms of probiotics are fully understood, different beneficial health effects related to the consumption of probiotics are proven and accepted by the scientific world. These effects have to be put in the framework of a healthy diet, prevention and an improvement of the general well being. In this short overview, some health-beneficial effects of the regular ingestion of the probiotic strain Lactobacillus casei Shirota by both healthy persons and subjects with specific complaints is reported.

Cultured Milk Products↗