The arcB gene of Escherichia coli encodes a sensor-regulator protein for anaerobic repression of the arc modulon

The arcA (dye) and arcB genes of Escherichia coli are responsible for anaerobic repression of target operons and regulons of aerobic function (the arc modulon). The amino acid sequence of ArcA (Dye) indicated that it is the regulator protein of a two-component control system. Here we show that ArcB is a membrane sensor protein on the basis of its deduced amino acid sequence (778 residues), hydropathicity profile, and cellular distribution. On the carboxyl end of the ArcB sequence there is an additional domain showing homology with conserved regions of regulator proteins. Deletion into this domain destroyed ArcB function. ArcB conserved a histidine residue for autophosphorylation of the sensor proteins, and aspartic residues important for the regulator proteins.     

厦门附近海域浮游甲藻类的分布

本文报道了厦门附近海域浮游甲藻类49种,并对其生态特性以及与海洋环境因素的关系进行了详细研究与讨论。分析的204号样品,系1980年9月至1981年8月,逐月采自厦门海域的浔江区(Ⅰ区),西港区(Ⅱ区)和九龙江口区(Ⅱ区)。     

罗汉果组培苗的栽培研究

本文报道罗汉果组培苗的栽培研究结果,为罗汉果在生产上推广应用组培苗栽培,提供有效的技术措施。     

国产磨芋属的染色体核型报道(1)

本文报道了磨芋属(Amorphophallus Blume)六个种的染色体数目和核型,其中5个种属于首次报道。其核型公式如下: 1.滇磨芋 K(2n)=2x=26=26m.2.磨芋 K(2n)=2x=26=26m.3.攸落磨芋K(2n)=2x=26=22m(2SAT)+4sm.(2SAT).4.西盟磨芋 K(2n)=2x=26=20m+4sm+2st.5.勐海磨芋 K(2n)=2x=26=22m+4sm.6.白磨芋 K(2n)=2x=26=20m(2SAT)+6sm。     

桂西壮族手皮纹的分析

本文对广西西部500例健康壮族大、中学生的手皮纹进行了观察分析,计算出各型指纹频率、指纹脊线总数、指纹频度指数、atd角度、a-b脊线数、τ距比、主线横向指数、皮纹花样出现率、掌褶纹出现率共九项基本参数,并将这些数值与汉族作了比较,桂西壮族的手纹与汉族既有相似之处,又有本民族的特点。     

DA/DAPI-Fluorescent heteromorphism of human Y chromosome

Summary Variation of DA/DAPI intensity in the Yq12 band was observed in five amniotic cell specimens and one blood specimen from the father of one fetus. Three distinct classes of Yq heterochromatin were identified by distamycin A (DA) treatment of the cell cultures and various staining techniques. The heterochromatin in the Yq11.23 sub-band does not under-condense when exposed to DA, and shows pale fluorescence with quinacrine staining, positive C-banding, and bright fluorescence with DA/DAPI technique. This class of heterochromatin was consistently observed in all specimens studied. The other two classes of heterochromatin are in the Yq12 band. Both show undercondensation when exposed to DA, quinacrine-bright fluorescence, and positive C-banding; howover, one class of heterochromatin shows DA/DAPI-bright fluorescence and the other shows pale fluorescence. The size and banding intensity of the two classes of heterochromatin in Yq12 are variable. These results provide cytological evidence of heterogeneity within the Y heterochromatin region containing AT-rich DNA.     

A cytogenetic study of mentally retarded school children in taiwan with special reference to the fragile X chromosome

Summary A cytogenetic study was made on 341 mentally retarded children in the Provincial Nantou Rehabilitation Center for the Mentally Retarded and the St. Raphael Opportunity Center in Tainan. Of the 89 mentally retarded children with chromosomal abnormalities, 63 had Down syndrome, 13 had the fragile X [fra(X)] syndrome, and the remaining had other aneuploid constitutions. Family studies were possible for 2 of the 13 fra(X) probands. The results of this study illustrate the contribution of chromosomal abnormalities to the pathogenesis of mental retardation in children.     

Genetic transformation in Lactobacillus sp. strain 100-33 of the capacity to colonize the nonsecreting gastric epithelium in mice

Lactobacillus isolates able to colonize the surfaces of the nonsecreting epithelia in the stomachs of monoassociated ex-germfree mice were derived from Lactobacillus acidophilus 100-33. Strain 100-33 was originally isolated from pig feces and is unable to colonize the murine gastric epithelium. In experiments involving attempts genetically to transform the capacity to colonize the epithelium, cells of strain 100-33 were treated with muralytic enzymes and mixed with polyethylene glycol and genomic or plasmid DNA extracted from Lactobacillus fermentum RI. Strain RI was originally isolated from a conventional mouse and has the capacity to colonize the nonsecreting gastric epithelium. The mixtures containing cells, polyethylene glycol, and DNA were plated on a regeneration medium. After overnight incubation, the cells were washed from the plates and introduced by gastric gavage into germfree mice. Only mice that received regenerated 100-33 cells previously mixed with genomic DNA from strain RI had layers of gram-positive bacteria on the keratinized epithelia of their stomachs. Six isolates cultured from the washed gastric tissues of these animals were characterized. When a culture of each or a pool of cultures of the six were orally administered to germfree mice, layers of gram-positive bacterial cells were visible on the keratinized gastric epithelia of the animals within 1 to 3 weeks. Cells of all six, but not of strain 100-33, reacted with antibody made in rabbits to L. fermentum RI cells, as determined by an enzyme-linked immunosorbent assay. Nevertheless, all six had fermentation profiles identical to that of strain 100-33.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of metal ions on the fluorescence of leucine aminopeptidase and its dansyl-peptide substrates

The effect of Cu(II), Ni(II), Zn(II), Mg(II), and Mn(II) on the fluorescence of porcine kidney cytosol leucine aminopeptidase and three of its dansyl(Dns) peptide substrates, Leu-Gly-NHNH-Dns, Leu-Gly-NH(CH2)2NH-Dns, and Leu-Gly-NH(CH2)6NH-Dns, has been investigated. These five metal ions were chosen for study because each binds to the regulatory metal binding site of leucine aminopeptidase. Since the binding is relatively weak, kinetic studies of the different metalloderivatives of the enzyme are normally carried out in the presence of large molar excesses of these metal ions that can potentially affect both the enzyme and substrate. The fluorescence of all of the dansyl-peptides, as well as several other dansyl species, is quenched by Ni(II) and Cu(II), but not by Mg(II), Mn(II), or Zn(II). The absorption spectra of these dansyl substrates are also perturbed by Ni(II) and Cu(II). The rate at which maximal quenching for some dansyl species is attained after mixing with Ni(II) and Cu(II) is slow and the quenching is reversed on addition of EDTA. These results indicate that the quenching is the result of complex formation between the fluorophores and these metal ions. The association constants for the metal complexes have been determined from Stern-Volmer plots. In addition to complex formation, Ni(II) and Cu(II) cause the degradation of Leu-Gly-NHNH-Dns through a two step mechanism involving loss of dansic acid. Ni(II) and Cu(II) also partially quench the fluorescence of leucine aminopeptidase through contact with its surface accessible Trp residues. These observations indicate that care must be taken in stopped flow fluorescence studies of reactions between this enzyme and its dansyl substrates to avoid adverse effects brought about by Ni(II) and Cu(II).