Assembly of yeast Sec proteins involved in translocation into the endoplasmic reticulum into a membrane-bound multisubunit complex

Secretory-protein translocation into the endoplasmic reticulum (ER) is thought to be catalysed by integral membrane proteins. Genetic selections uncovered three Saccharomyces cerevisiae genes (SEC61, SEC62 and SEC63), mutations in which block import of precursor proteins into the ER lumen in vivo and in vitro. The DNA sequences of SEC62 and SEC63 predict multispanning membrane proteins, and biochemical characterization of the SEC62 protein (Sec62) confirms that it is an integral ER membrane protein. Here we show that Sec61, Sec62 and Sec63 are assembled with two additional proteins into a multisubunit membrane-associated complex. These results confirm previous predictions, based upon genetic interactions between the SEC genes, that Sec61, Sec62 and Sec63 act together to facilitate protein translocation into the ER.     

Inhibition of rat adjuvant arthritis by a new immunosuppressive agent rubidomycin

Résumé Un nouveau composé anthracyclique à propriétés antibiotiques et cytotoxiques, la Rubidomycine (Daunomycine), a été administré à des rats peu après injection intra-dermique d'adjuvant complet de Freund. Par comparaison avec un groupe témoin qui a été traité avec un autre antibiotique, la tétracycline, non réputé cytotoxique, on a constaté une réduction marquée des lésions systémiques et de l'arthrite de la maladie provoquée par l'adjuvant.

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Work conducted during the tenure of a Nuffield Research Fellowship.

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Junior Fellow, Medical Research Council.     

Effect of nerve stimulation,denervation, and duct ligation,on kallikrein content and duct cell granules of the cat's submandibular gland

Summary Various procedures which reduce or deplete the kallikrein content of the cat's submandibular gland correspondingly reduce the number of apical granules in the striated duct cells. The kallikrein content is greatly reduced after chronic parasympathetic but not after sympathetic nerve section which suggests that the parasympathetic innervation is required for synthesis or storage of this enzyme.We wish to acknowledge the valuable assistance of Dr T. Nihei and Mr. J. Wimal in some of the enzyme measurements.This work was supported by grants from the Medical Research Council of Canada and the Alberta Heart Foundation.     

Ferromagnetism of a graphite nodule from the Canyon Diablo meteorite

There are recent reports of weak ferromagnetism in graphite and synthetic carbon materials such as rhombohedral C(60) (ref. 4), as well as a theoretical prediction of a ferromagnetic instability in graphene sheets. With very small ferromagnetic signals, it is difficult to be certain that the origin is intrinsic, rather than due to minute concentrations of iron-rich impurities. Here we take a different experimental approach to study ferromagnetism in graphitic materials, by making use of meteoritic graphite, which is strongly ferromagnetic at room temperature. We examined ten samples of extraterrestrial graphite from a nodule in the Canyon Diablo meteorite. Graphite is the major phase in every sample, but there are minor amounts of magnetite, kamacite, akaganéite, and other phases. By analysing the phase composition of a series of samples, we find that these iron-rich minerals can only account for about two-thirds of the observed magnetization. The remainder is somehow associated with graphite, corresponding to an average magnetization of 0.05 Bohr magnetons per carbon atom. The magnetic ordering temperature is near 570 K. We suggest that the ferromagnetism is a magnetic proximity effect induced at the interface with magnetite or kamacite inclusions.     

The genome of the simian and human malaria parasite Plasmodium knowlesi

Plasmodium knowlesi is an intracellular malaria parasite whose natural vertebrate host is Macaca fascicularis (the 'kra' monkey); however, it is now increasingly recognized as a significant cause of human malaria, particularly in southeast Asia. Plasmodium knowlesi was the first malaria parasite species in which antigenic variation was demonstrated, and it has a close phylogenetic relationship to Plasmodium vivax, the second most important species of human malaria parasite (reviewed in ref. 4). Despite their relatedness, there are important phenotypic differences between them, such as host blood cell preference, absence of a dormant liver stage or 'hypnozoite' in P. knowlesi, and length of the asexual cycle (reviewed in ref. 4). Here we present an analysis of the P. knowlesi (H strain, Pk1(A+) clone) nuclear genome sequence. This is the first monkey malaria parasite genome to be described, and it provides an opportunity for comparison with the recently completed P. vivax genome and other sequenced Plasmodium genomes. In contrast to other Plasmodium genomes, putative variant antigen families are dispersed throughout the genome and are associated with intrachromosomal telomere repeats. One of these families, the KIRs, contains sequences that collectively match over one-half of the host CD99 extracellular domain, which may represent an unusual form of molecular mimicry.