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1.
Congenic anti-Lyt-3.1 sera have recently been produced by immunizing B6-Lyt-2a mice with thymocytes from either B6-Lyt-2a, Lyt-3a or B6-Lyt-2a, Lyt-3a, H-2k mice (Boos et al. 1978). Surprisingly, mice of the congenic strain B6 failed to produce either anti-Lyt-2.1 or anti-Lyt-3.1 cytotoxic antibodies after identical immunizations. To determine the genetic basis for the difference in response to Lyt-3.1, (B6 × B6-Lyt-2a)Fa mice and progeny of the backcross, (B6 × B6-Lyt-2a)F1 × B6-Lyt-2a, were immunized with B6-Lyt-2a, Lyt-3a, H-2k thymocytes. In addition, thymic biopsies of backcross progeny were performed and thymocytes tested for the Lyt-2.2 antigenic specificity. Results indicate that gene(s) governing the immune response to Lyt-3.1 is (are) linked to theLyt-2 locus, and that the responder allele (linked toLyt-2 a ) shows very poor penetrance in Lyt-2a/Lyt-2b mice. 相似文献
2.
Sequence of the mglB gene from Escherichia coli K12: comparison of wild-type and mutant galactose chemoreceptors 总被引:1,自引:0,他引:1
Annette Scholle Jörg Vreemann Volker Blank Annette Nold Winfried Boos Michael D. Manson 《Molecular & general genetics : MGG》1987,208(1-2):247-253
Summary The mglB gene of Escherichia coli codes for a galactose-binding protein (GBP) that serves both as the galactose chemoreceptor and as the recognition component of the -methylgalactoside transport system. The mglB551 mutation eliminates the chemotactic function of GBP without altering its transport or substrate-binding properties. To investigate the interaction between GBP and Trg, the chemotactic signal transducer for galactose, we sequenced the mglB genes from wild-type and mglB551 mutant strains. The mutation causes the replacement of Gly74 of GBP by Asp. This residue is located in alpha-Helix III at the tip of the P domain in the GBP tertiary structure farthest removed from the substrate-binding cleft between the P and Q domains. We conclude that Helix III must be part of, or at least adjacent to, the recognition site for Trg. Our sequence also included part of the mglA gene, which is immediately distal to mglB. The amino acid sequence deduced for the beginning of the MglA protein showed homology with a family of polypeptides that contain an ATP-binding site and are components of binding-protein-dependent transport systems. 相似文献
3.
Michael K. Dahl Eric Francoz William Saurin Winfried Boos Michael D. Manson Maurice Hofnung 《Molecular & general genetics : MGG》1989,218(2):199-207
Summary The malE and malK genes from Salmonella typhimurium, and the MalEFG operon and a portion of malK from Enterobacter aerogenes were cloned and sequenced. Plasmid-borne malE genes from both species and the malF and malG genes from E. aerogenes were expressed normally in Escherichia coli, and their products function in maltose transport. This shows that the malB products from the three species are interchangeable, at least in the combinations tested. The general genetic organization of the malB region is conserved. Potential binding sites and distances between them are highly conserved in the regulatory intervals. An unexpected conserved region was detected, which we call the U box, and which could be another target for a regulatory protein. This hypothesis is supported by the presence of the U box in the regulatory, region of the pulA-malX operon in Klebsiella pneumoniae. The intergenic region between malE and malF from S. typhimurium and E. aerogenes, contains inverted repeats similar to the palindromic units (PU or REP) found at the same location in E. coli. The predicted amino acid sequence of the encoded proteins showed 90% or more identity in every pairwise comparison of species. 相似文献
4.
At high osmolarity, Escherichia coli synthesizes trehalose intracellularly, irrespective of the nature of the carbon source. Synthesis proceeds via the transfer of UDP-glucose to glucose 6-phosphate, yielding trehalose 6-phosphate, followed by its dephosphorylation to trehalose (H.M. Giaeyer, B.O. Styrvold, I. Kaasen, and A.R. Str?m, J. Bacteriol. 170:2841-2849, 1988). This reaction was exploited to preparatively synthesize [14C]trehalose from exogenous [14C]glucose by using intact bacteria of a mutant (DF214) that could not metabolize glucose. The total yield of radiochemically pure trehalose from glucose was routinely more than 50%. 相似文献
5.
Both uterine horns of 14 dairy cows with ovarian follicular cysts, and four animals affected with purulent endometritis were flushed via catheter using 30 ml phosphate buffered saline, following evisceration at a local abattori. Activity in the flushing media of alkaline phosphatase (ALP) and aspartate aminotransferase (GOT) were examined. Ovaries were prepared for light microscopy. Amount and morphological integrity of luteinized tissue found on the ovaries were reflected by correspondent levels in ALP activity, which was higher in the media taken from the ipsilateral to the luteal tissue situated uterine horns (651 +/- 228 vs 244 +/- 62 u/l, n = 3). Only cows having relatively large amounts of luteal tissue on the cystic ovaries (as in luteinized follicular cysts) exhibited very high ALP activity in uterine flushings (2693 +/- 1348 u/l, n = 2). Results suggest the existence of local relationships between luteal tissue in the ovary and the ipsilateral uterine horn in cows with ovarian follicular cysts. 相似文献
6.
7.
A Boos W Meyer I Peukert-Adam R Schwarz E Grunert 《Gegenbaurs morphologisches Jahrbuch》1988,134(2):189-204
Genital organs and blood were obtained from dairy cows at a local abattoir. 3 recently ovulated follicles and 20 corpora lutea of estrous cycle (CLC) were used for the quantitative enzyme histochemical demonstration of delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-OHSDH), succinate dehydrogenase (SDH) and glucose-6-phosphate dehydrogenase (G-6-PDH) activity, employing a computerized microscope photometer. Progesterone was determined in blood serum by radioimmunoassay. Luteal tissue was grouped into several stages of development according to micromorphological criteria. Activities per volume unit of 3 beta-OHSDH and SDH in large luteal cells (LLC), as well as in small luteal cells (SLC), and luteal tissue (LT), relative amounts of the 3 beta-OHSDH-positive tissue fraction (PLCC), and progesterone concentrations in blood serum exhibited a significant pattern corresponding to the morphological development of the endocrine gland. G-6-PDH showed an increase in activity per volume unit during tissue development lasting until the beginning of regressive changes, and as significant in LLC and LT. Activities per volume unit of 3 beta-OHSDH (p less than or equal to 0.001) and SDH (p less than or equal to 0.01) were higher in LLC than in SLC, indicating superior steroidogenic capacities, while G-6-PDH activity was distinctly higher in the latter (p less than or equal to 0.001). Almost all parameters tested were correlated positively. 3 beta-OHSDH and SDH exhibited a significantly positive correlation in LLC (p less than or equal to 0.01) and LT (p less than or equal to 0.001) during periods of measureable progesterone secretion. In SLC this correlation was nonsignificant (p greater than 0.05). G-6-PDH showed a relative poor correlation to 3 beta-OHSDH (LLC, p less than or equal to 0.05; LT, p less than or equal to 0.01) and SDH (LT, p less than or equal to 0.05). Enzyme activities in LLC as well as in SLC were generally positively correlated (p less than or equal to 0.001). All enzymes tested exhibited a significantly positive correlation with progesterone concentrations in blood serum. This was significant for SDH only during measurable progesterone secretion, and less marked for G-6-PDH. 相似文献
8.
Ca2+ treatment renders the outer membrane of Escherichia coli reversibly permeable for macromolecules. We investigated whether Ca2+-induced uptake of exogenous protein into the periplasm occurs by mechanisms similar to Ca2+-induced uptake of DNA into the cytoplasm during transformation. Protein import through the outer membrane was monitored by measuring reconstitution of maltose transport after the addition of shock fluid containing maltose-binding protein. DNA import through the outer and inner membrane was measured by determining the efficiency of transformation with plasmid DNA. Both processes were stimulated by increasing Ca2+ concentrations up to 400 mM. Plasmolysis was essential for a high efficiency; reconstitution and transformation could be stimulated 5- and 40-fold, respectively, by a high concentration of sucrose (400 mM) in cells incubated with a suboptimal Ca2+ concentration (50 mM). The same divalent cations that promote import of DNA (Ca2+, Ba2+, Sr2+, Mg2+, and Ni2+) also induced import of protein. Ca2+ alone was found to be inefficient in promoting reconstitution; successive treatment with phosphate and Ca2+ ions was essential. Transformation also was observed in the absence of phosphate, but could be stimulated by pretreatment with phosphate. The optimal phosphate concentrations were 100 mM and 1 to 10 mM for reconstitution and transformation, respectively. Heat shock, in which the cells are rapidly transferred from 0 to 42 degrees C, affected the two processes differently. Incubation of cells at 0 degrees C in Ca2+ alone allows rapid entry of protein, but not of DNA. Transformation was observed only when exogenous DNA was still present during the heat shock. Shock fluid containing maltose-binding protein inhibited transformation (with 6 microgram of DNA per ml, half-maximal inhibition occurred at around 300 microgram of shock fluid per ml). DNA inhibited reconstitution (with 5 microgram of shock fluid per ml, half-maximal inhibition occurred at around 3 mg of DNA per ml). 相似文献
9.
10.
Characterization of the ugp region containing the genes for the phoB dependent sn-glycerol-3-phosphate transport system of Escherichia coli 总被引:8,自引:0,他引:8
Summary The ugp structural genes, coding for the pho regulon dependent sn-glycerol-3-phosphate transport system, were cloned in pBR322 and characterized. The expression of the cloned ugp system was phoB dependent. Cells containing the ugp plasmid overproduced the G3P binding protein upon phosphate starvation. Tn5 mutagenesis of the cloned DNA revealed that the ugp genes are organized in two separate operons which comprise at least four genes: ugpB and ugpD constitute one operon, ugpA and ugpC constitute the other. The structural gene for the G3P binding protein (G3PBP) is ugpB.The ugpC gene product was also synthesized in minicells as a polypeptide, with an apparent molecular weight of 40,000. No gene products could be assigned to the ugpA and ugpD genes. Hybridization experiments allowed the physical characterization of 20 kb of DNA adjacent to the ugp genes on the E. coli chromosome including the liv genes. 相似文献