Mutational analysis of a conserved motif of Agrobacterium tumefaciens VirD2

The VirD2 polypeptide from Agrobacterium tumefaciens, in the presence of VirD1, introduces a site- and strand-specific nick at the T-DNA borders. A similar reaction at the origin of transfer (oriT) of plasmids is essential for plasmid transfer by bacterial conjugation. A comparison of protein sequences of VirD2 and its functional homologs in bacterial conjugation and in rolling circle replication revealed that they share a conserved 14 residue segment, HxDxxx(P/u)HuHuuux [residues 126-139 of VirD2; Ilyina, T.V. and Koonin, E.V. (1992) Nucleic Acids Res. 20, 3279-3285]. A mutational approach was used to test the role of these residues in the endonuclease activity of VirD2. The results demonstrated that the two invariant histidine residues (H133 and H135) are essential for activity. Mutations at three sites, histidine 126, aspartic acid 128 and aspartic acid 130, that are conserved in a subfamily of the plasmid mobilization proteins, led to the loss of VirD2 activity. Aspartic acid at position 130, could be substituted with glutamic acid and to a much lesser extent, with tyrosine. In contrast, another conserved residue, asparagine 139, tolerated many different amino acid substitutions. The non-conserved residues, arginine 129, proline 132 and leucine 134, were also found to be important for function. Isolation of null mutations that map throughout this conserved domain confirm the hypothesis that this region is essential for function.

Mycobacterium tuberculosis infection in an orangutan (Pongo pygmaeus)

A respiratory disorder was noted in a 5-year-old female orangutan kept in the Yongin Farmland. Radiographically, multiple radiodense foci ranging from 2 to 6 mm diameter were seen throughout the lung lobes. Grossly, the thoracic cavity revealed a firm texture and grayish-pink discoloration of the left apical lung lobe. Histopathologically, multifocal areas of granulomatous pneumonia present the right and left apical lung lobes. Both primers from IS1081 and IS6110 targeting 196 bp and 245 bp respectively were used in polymerase chain reaction, Mycobacterium tuberculosis was isolated from liver and confirmed by polymerase chain reaction.

Molecular characterization of two Drosophila guanylate cyclases expressed in the nervous system

We have isolated, by interspecies hybridization, two classes of Drosophila cDNA each encoding a different guanylate cyclase (GC). One of them encodes an alpha subunit homolog of soluble GC, designated DGC alpha 1, and the other encodes a receptor-type GC, designated DrGC. The dgc alpha 1 cDNA encodes a protein of 676 amino acids and maps to 99B. In situ hybridization to adult tissue sections showed that dgc alpha 1 mRNA is found mainly in the cell bodies of the optic lobe, central brain, and thoracic ganglia. The DGC alpha 1 protein was also localized primarily to the nervous system by immunocytochemical staining, consistent with results of in situ hybridization. However, no detectable expression of this protein was found in the retina. The other class of cDNA, drgc, maps to 76C and encodes a 1525-amino acid protein displaying structural features similar to other known receptor-type guanylate cyclases. However, it has a C-terminal 430 amino acid region that has no homology to any known proteins. drgc RNA is expressed at low levels throughout development and in adult heads and bodies. In situ hybridizations to adult tissue sections showed that drgc mRNA is expressed in a wide range of tissues, including the optic lobe, central brain, thoracic ganglia, digestive tract, and the oocyte.

Isolation and characterization of the gene encoding the Drosophila melanogaster transcriptional elongation factor, TFIIS

We have characterized a genomic clone encoding the Drosophila melanogaster transcriptional elongation factor, TFIIS. The coding region of the TFIIS gene is interrupted by a short intron. The potential promoter region, deduced from the determination of the transcription start point (tsp), lacks distinct TATAAA or CCAAT box consensus sequences. Southern analysis and the in situ hybridization to chromosomes suggests that it is single-copy gene which is localized to the 35B region on the left arm of the second chromosome.

Fatal vascular involvement in systemic lupus erythematosus following epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita may be associated with various systemic diseases, including systemic lupus erythematosus. We describe the clinical and immunological findings in a 38-year-old women with epidermolysis bullosa acquisita and systemic lupus erythematosus. The epidermolysis bullosa acquisita preceded a dramatic flare of systemic lupus erythematosus and fatal cerebral vasculitis. If serologic evidence of lupus erythematosus develops during the course of epidermolysis bullosa acquisita, a thorough investigation is warranted to rule out potentially life-threatening systemic lupus erythematosus.

Torsade de pointes induced by terfenadine in a patient with long QT syndrome

Torsade de pointes is a form of polymorphic ventricular tachycardia that is associated with prolongation of the QT interval. Although torsade de pointes is found in many clinical settings, it is mostly drug induced. Similar problems have been described with nonsedating H1-receptor antagonists, such as astemizole and terfenadine. Terfenadine is a widely used antihistamine. The authors report a case of torsade de pointes in a patient with a possible congenital sporadic form of QT interval prolongation who was receiving a therapeutic dose of terfenadine.

Suprageneric classification of peptidoglycan group B actinomycetes by nucleotide sequencing of 5S ribosomal RNA

5S ribosomal RNA sequences were determined for thirteen actinomycetes mainly representatives with the rare group B type peptidoglycan. The primary and secondary structure of the resultant sequences were of the type characteristic of Gram-positive bacteria with DNA rich in guanine plus cytosine. The sequencing and associated chemotaxonomic data provide compelling grounds for classifying actinomycetes with a group B type peptidoglycan in a single family. The family Microbacteriaceae fam. nov. is proposed to accommodate actinomycetes classified in the genera Agromyces, Aureobacterium, Clavibacter, Curtobacterium and Microbacterium.

Fluorescent chemosensing of catechol and catecholamines in water

It has been known for almost 35 years that catechol complexes reversibly to boronic acids. We observe that 2-anthrylboronic acid complexes catechol in water with Kd 330 microM and concomitant 20-fold reduction in fluorescence intensity. L-DOPA and dopamine behave similarly, suggesting a mechanism for the development of real-time sensing schemes.

Evidence for adaptive evolution of the G6pd gene in the Drosophila melanogaster and Drosophila simulans lineages

Proponents of the neutral theory argue that evolution at the molecular level largely reflects a process of random genetic drift of neutral mutations. Under this theory, levels of interspecific divergence and intraspecific polymorphism are expected to be correlated across classes of nucleotide or amino acid sequences with different degrees of functional constraint, such as synonymous and replacement sites. Nucleotide sites with reduced polymorphism should show comparably reduced levels of interspecific divergence. To examine this hypothesis, we have sequenced 32 and 12 copies of the glucose-6-phosphate dehydrogenase (G6pd) gene in Drosophila melanogaster and Drosophila simulans, respectively. Both species exhibit similar levels of nucleotide polymorphism at synonymous sites. D. melanogaster shows two amino acid polymorphisms, one associated with the cosmopolitan allozyme polymorphism and a second with an allozyme polymorphism endemic to European and North African populations. In contrast, D. simulans shows no replacement polymorphism. While synonymous divergence between species is 10%, which is typical of other genes, there are 21 replacement differences. This level of amino acid sequence divergence, when contrasted with levels of amino acid polymorphism, silent polymorphism, and divergence, is in 10-fold excess over that expected under the neutral model of molecular evolution. We propose that this excess divergence reflects episodes of natural selection on G6pd resulting in fixation of advantageous amino acid mutations in these two recently separated lineages.

Relapsing syphilis

Although penicillin still remains highly effective for syphilis, concerns have been raised that current regimens may be inadequate for the treatment of early syphilis. We report the failure of benzathine penicillin in the treatment of secondary syphilis. Extensive tracing of sexual contact history failed to identify sources of possible reinfection; therefore, we believe that this case represents a treatment failure and an ensuing relapse of secondary syphilis.

Sea urchin maternal mRNA classes with distinct development regulation

Previous studies of newly synthesized proteins during early development in sea urchins have revealed several different patterns of synthesis that can be used to predict the existence of mRNA classes with distinct regulatory controls. We have identified clones for abundant maternal mRNAs that are actively translated during early development by screening a cDNA library prepared from polysomal poly(A)+RNA isolated from 2-cell stage (2-hour) Strongylocentrotus purpuratus embryos. Probes prepared from these cDNA clones and several previously characterized maternal mRNA cDNAs were used to compare relative levels of individual mRNAs in eggs and embryos and their translational status at various developmental stages. These abundant mRNAs can be classified into two major groups which we have termed cleavage stage-specific (CSS) and post cleavage stage (PCS) mRNAs. The relative levels of the CSS mRNAs are highest during the rapid cleavage stage and decrease dramatically at the blastula stage (12-hours). In contrast, PCS mRNAs are present at relatively low levels during the rapid cleavage stage and then increase at the blastula stage. Polysome partition profiles reveal that CSS mRNAs are translated more efficiently than PCS mRNAs in the unfertilized egg, at fertilization, and during the cleavage stages. Following the blastula stage, some CSS transcripts move out of polysomes and accumulate as untranslated RNAs, while newly transcribed PCS mRNAs are recruited into polysomes. These data suggest that the rapid cell cycles following fertilization require high levels of specific cleavage stage proteins, and the synthesis of these proteins occurs preferentially over PCS mRNAs.

A Drosophila phospholipase C gene that is expressed in the central nervous system

A Drosophila phospholipase C (PLC) gene, designated as plc-21, was isolated by screening a genomic DNA library using a cDNA for a previously isolated Drosophila PLC gene, norpA, as probe under reduced stringency hybridization conditions. The gene maps to 21C on the left arm of the second chromosome. Two proteins of 1305 and 1312 amino acids, respectively, were deduced from two classes of cDNA which were isolated. The two putative plc-21 proteins are similar in sequence and overall structure to the beta-class of PLCs found in mammals and differ from each other only by 7 amino acid residues that are present near the C terminus of one of the proteins but not the other. Hybridization of plc-21 cDNA probes to blots of poly(A)+ RNA revealed that the gene encodes a 7.0-kilobase transcript that could be detected in the head but not in the body of adult flies and a 5.6-kilobase transcript that could be detected throughout development and in both heads and bodies of adults. In situ hybridization of cDNA sequences to tissue sections showed that the gene is expressed in the neuronal cell bodies of the optic lobe, central brain, and thoracic ganglia of adults and the brain of larvae. This tissue distribution of plc-21 transcripts is identical to the distribution of transcripts from a Drosophila Go alpha-subunit gene that we reported previously.

Molecular characterization of Drosophila gene encoding G0 alpha subunit homolog

A Drosophila melanogaster gene (dgo) encoding a G protein alpha subunit has been isolated by screening genomic and adult head cDNA libraries using bovine transducin alpha subunit cDNA as probe. The gene, which maps to 47A on the second chromosome, encodes two proteins which are both 354 amino acids long but differ in seven amino acids in the amino-terminal region. The deduced amino acid sequences of the two proteins are 81% identical to that of a rat Go alpha subunit. Analysis of genomic clones revealed that there are eight coding exons and that the putative transcripts for the two proteins differ in the 5'-noncoding regions and the first coding exons but share the remaining six coding exons. The arrangement of two different 5'-noncoding regions on the gene suggests that two different promoters regulate the expression of the transcripts encoding the two proteins. RNA blot analysis detected three transcripts: a 3.9-kilobase (kb) transcript found at all stages of development; a 5.4-kb transcript present predominantly in adult heads; and a 3.4-kb transcript present only in adult bodies. In situ hybridizations of a cDNA probe to adult tissue sections showed that the gene is expressed abundantly in neuronal cell bodies in the brain, optic lobe, and thoracic ganglia.

Mechanism of suppression in Drosophila: regulation of tryptophan oxygenase by the su(s)+ allele

The suppressor gene, su(s)2, in Drosophila melanogaster restores the production of red and brown eye pigments for some purple and vermilion mutant alleles, respectively. We showed previously that the product of the su(s)+ allele caused inhibition of the sepiapterin synthase A produced by the purple mutant but did not affect the wild-type enzyme. Suppression was accomplished by removing su(s)+ from the genome. We now report that the tryptophan oxygenase, produced by suppressible vermilion alleles, is also inhibited by extracts from su(s)+ flies. The inhibition of the vermilion enzyme can be reduced or eliminated, respectively, by prior storage of the extract at 4 or -20 degrees C or by boiling, whereas the wild-type enzyme is not affected by extracts of su(s)+ flies. Also, when the suppressible vermilion strain is raised on certain diets, brown eye pigment production occurs. This epigenetic suppression was reduced by the presence of an extra copy of su(s)+ in the genome. These data support a posttranslational mechanism for regulation of enzyme activity in which the activity of the mutant enzyme is reduced by the product of the su(s)+ allele. How the su(s)+ gene product can distinguish between the normal and the mutant forms of these two enzymes is discussed, along with other mechanisms for suppression that are currently under investigation.

Messenger RNA structure participating in the initiation of synthesis of cucumber mosaic virus coat protein

The sequence of the 5'-terminal 106 nucleotides of cucumber mosaic virus (strain Y) RNA 4, the mRNA coding for viral coat protein, has been determined. The first AUG was located at 77 nucleotides from the 5'-terminus and was confirmed to be an initiation codon by analysis of the N-terminal amino acid sequence of the protein. The nucleotide sequence (positions 77-106) beyond the AUG codon predicted the sequence of ten amino acids corresponding to the N-terminal region of the protein, which exactly matched the determined amino acid sequence containing an acetyl methionine as the N-terminal amino acid. The distance of the initiation codon AUG from the cap structure was 76 nucleotides and the longest among the mRNAs for coat protein of plant viruses so far reported (9-36 nucleotides). This noncoding region is rich in U residues (40%) and the number of G residues (21 nucleotides) is the largest among these mRNAs (usually 1 or 2 residues). A possible secondary structure is postulated for the region, which might be implicated in efficient translation of the RNA 4 in vivo.

Electron microscopy of renal and ocular changes in virus-induced diabetes mellitus in mice

The eyes, kidneys and pancreas of mice (SJL/J) infected with encephalomyocarditis virus were examined by light and electron microscopy. Diabetic mice with the longest duration (6 months) of diabetes showed marked renal and ocular alterations. Fasting blood glucose levels were 17.8-21.9 mmol/l and glycosuria was present. Clinically, based on ophthalmoscopy and fluorescein angiography, retinal vessels were normal. Histologically, moderately decreased numbers of pericytes were noted following trypsin digestion. The basement membrane of inner retinal vessels showed significant thickening in diabetic mice. Corneal epithelial oedema was present and surface microvillus projections were decreased compared with control mice. The kidneys of the same animals showed nodular and diffuse glomerulosclerosis and mesangial thickening. Electron microscopy showed excessive accumulation of basement membrane-like material in the mesangium and the peripheral glomerular region. Histologically, moderate to advanced kidney disease was associated with relatively early retinopathy.