Yersinia pestis, the cause of plague, is a recently emerged clone of Yersinia pseudotuberculosis

Plague, one of the most devastating diseases of human history, is caused by Yersinia pestis. In this study, we analyzed the population genetic structure of Y. pestis and the two other pathogenic Yersinia species, Y. pseudotuberculosis and Y. enterocolitica. Fragments of five housekeeping genes and a gene involved in the synthesis of lipopolysaccharide were sequenced from 36 strains representing the global diversity of Y. pestis and from 12–13 strains from each of the other species. No sequence diversity was found in any Y. pestis gene, and these alleles were identical or nearly identical to alleles from Y. pseudotuberculosis. Thus, Y. pestis is a clone that evolved from Y. pseudotuberculosis 1,500–20,000 years ago, shortly before the first known pandemics of human plague. Three biovars (Antiqua, Medievalis, and Orientalis) have been distinguished by microbiologists within the Y. pestis clone. These biovars form distinct branches of a phylogenetic tree based on restriction fragment length polymorphisms of the locations of the IS100 insertion element. These data are consistent with previous inferences that Antiqua caused a plague pandemic in the sixth century, Medievalis caused the Black Death and subsequent epidemics during the second pandemic wave, and Orientalis caused the current plague pandemic.

A local electrostatic change is the cause of the large-scale protein conformation shift in bacteriorhodopsin

During light-driven proton transport bacteriorhodopsin shuttles between two protein conformations. A large-scale structural change similar to that in the photochemical cycle is produced in the D85N mutant upon raising the pH, even without illumination. We report here that (i) the pKa values for the change in crystallographic parameters and for deprotonation of the retinal Schiff base are the same, (ii) the retinal isomeric configuration is nearly unaffected by the protein conformation, and (iii) preventing rotation of the C13—C14 double bond by replacing the retinal with an all-trans locked analogue makes little difference to the Schiff base pKa. We conclude that the direct cause of the conformational shift is destabilization of the structure upon loss of interaction of the positively charged Schiff base with anionic residues that form its counter-ion.

Direct Evidence for Rapid Degradation of Bacillus thuringiensis Toxin mRNA as a Cause of Poor Expression in Plants1

It is well established that the expression of Bacillus thuringiensis (B.t.) toxin genes in higher plants is severely limited at the mRNA level, but the cause remains controversial. Elucidating whether mRNA accumulation is limited transcriptionally or posttranscriptionally could contribute to effective gene design as well as provide insights about endogenous plant gene-expression mechanisms. To resolve this controversy, we compared the expression of an A/U-rich wild-type cryIA(c) gene and a G/C-rich synthetic cryIA(c) B.t.-toxin gene under the control of identical 5′ and 3′ flanking sequences. Transcriptional activities of the genes were equal as determined by nuclear run-on transcription assays. In contrast, mRNA half-life measurements demonstrated directly that the wild-type transcript was markedly less stable than that encoded by the synthetic gene. Sequences that limit mRNA accumulation were located at more than one site within the coding region, and some appeared to be recognized in Arabidopsis but not in tobacco (Nicotiana tabacum). These results support previous observations that some A/U-rich sequences can contribute to mRNA instability in plants. Our studies further indicate that some of these sequences may be differentially recognized in tobacco cells and Arabidopsis.

Constitutive activation of phototransduction by K296E opsin is not a cause of photoreceptor degeneration.

The missense mutation Lys-296-->Glu (K296E) in the rhodopsin gene produces an opsin with no chromophore binding site and therefore is not activated by light. Nevertheless, the mutant opsin constitutively activates transducin in vitro and causes photoreceptor degeneration in vivo, possibly by continuously activating the phototransduction cascade, analogous to constant exposure to environmental light. We studied the K296E mutation in eight lines of transgenic mice. Each line developed photoreceptor degeneration with the rate of degeneration increasing monotonically as the ratio of mutant:wild-type opsin mRNA increased. At no time in the course of degeneration was there endogenous light adaptation in the retina as measured by the electroretinogram. The mutant opsin was found to be invariably phosphorylated and stably bound to arrestin. Light-independent activation of transducin was demonstrated only after the removal of arrestin and dephosphorylation of K296E opsin. Thus, K296E opsin in vivo does not activate the phototransduction cascade because it is shut off by photoreceptor inactivation mechanisms. Our data show that the K296E mutation does not cause photoreceptor degeneration by continuous activation of phototransduction.

Fresh water-salt water density currents : a major cause of siltation in estuaries /

"April 1957."

Memorial meeting: Israel Friedlaender, Bernard Cantor whose lives were sacrificed July 5, 1920 in the cause of Israel ...

Mode of access: Internet.

An enquiry into the cause of the procrastination & delay attributed to the judicial proceedings of the House of Lords and the Court of Chancery /

Outline of a plan proposed for the improvement of the existing law in all cases of insolvency.

A letter to the Earl of Liverpool on the cause of our present embarrassment and distress : and the measures necessary for our effectual relief /

Mode of access: Internet.

A half century tribute to the cause of temperance.

Mode of access: Internet.

An inquiry into the small-pox, medical and political : wherein a successful method of treating that disease is proposed, the cause of pits explained /

Mode of access: Internet.

Some fundamentals in the study of nutrition : the cause of malnutrition and effects produced by malnutrition namely, disease : and elementary treatise prepared for use in the livestock feed industry /

Library's copy has author's autograph on cover slip.