Primary structure of alpha-subunit precursor of Torpedo californica acetylcholine receptor deduced from cDNA sequence

DNA sequences complementary to the Torpedo californica electroplax mRNA coding for the alpha-subunit precursor of the acetylcholine receptor were cloned. The nucleotide sequence of the cloned cDNA indicates that the precursor consists of 461 amino acids including a prepeptide of 24 amino acids. Possible sites for acetylcholine binding and antigenic determinants on the alpha-subunit molecule are discussed.     

A reversibly antigen-responsive hydrogel.

Stimuli-responsive hydrogels that undergo abrupt changes in volume in response to external stimuli such as pH, temperature and solvent composition have potential applications in biomedicine and the creation of 'intelligent' materials systems, for example as media for drug delivery, separation processes and protein immobilization. Hydrogels have been reported that respond to pH, temperature, electric fields and saccharides. For some biomedical applications it would be very useful to have a material whose swelling response was dictated by a specific protein. Here we report such a material, which swells reversibly in a buffer solution in response to a specific antigen. The hydrogel was prepared by grafting the antigen and corresponding antibody to the polymer network, so that binding between the two introduces crosslinks in the network. Competitive binding of the free antigen triggers a change in gel volume owing to breaking of these non-covalent crosslinks. In addition, we show that the hydrogel displays shape-memory behaviour, and that stepwise changes in antigen concentration can induce pulsatile permeation of a protein through the network.     

Retroviral gag and DNA endonuclease coding sequences in IgE-binding factor gene

Immunoglobulin-binding factors are known to regulate the synthesis of B-cell-derived immunoglobulin heavy-chain isotypes. Cloning and nucleotide sequence determination of complementary DNA encoding rodent IgE-binding factors (IgE-BF) revealed that messenger RNA encodes a glycoprotein of 557 amino acids which is expressed as a precursor of relative molecular mass (Mr) 60,000 (60K) in COS7 monkey cells. We report here that the 3' two-thirds of the IgE-BF coding sequence shows a surprising homology (72%) at the DNA level with coding sequences of the gag and pol (DNA endonuclease) genes of the Syrian hamster intracisternal A particle (IAP H18), an endogenous retrovirus. This marked homology demonstrates that the rodent gene encoding IgE-BF is a hybrid gene which evolved very recently by integrating genes of viral origin, and that the encoded polypeptide comprises three separate domains: an IgE-BF domain and retrovirus-derived gag and DNA endonuclease-like domains. This may represent the first report of a cellular gene containing a virus-derived coding sequence.     

Transplantation of an entire muscle in mice

Zusammenfassung Bei Mäusegeschwistern führte homoplastische Transplantation kleiner Muskeln in toto zur Wiedererlangung ihrer vollen Funktion unter nervöser Kontrolle.

---

---

We thank ProfessorM. Otsuka, Dr.H. Ishikawa and Dr.E. Ozawa for their helpful suggestions and discussions and ProfessorM. Kuno for his review on this paper. We are also indebted to the Central Institute for Experimental Animals (Tokyo) for providing the mice.     

Reductive evolution suggested from the complete genome sequence of a plant-pathogenic phytoplasma

The minimal gene set essential for life has long been sought. We report the 860-kb genome of the obligate intracellular plant pathogen phytoplasma (Candidatus Phytoplasma asteris, OY strain). The phytoplasma genome encodes even fewer metabolic functions than do mycoplasma genomes. It lacks the pentose phosphate cycle and, more unexpectedly, ATP-synthase subunits, which are thought to be essential for life. This may be the result of reductive evolution as a consequence of life as an intracellular parasite in a nutrient-rich environment.     

An early extrasolar planetary system revealed by planetesimal belts in beta Pictoris

beta Pictoris (beta Pic) is a main-sequence star with an edge-on dust disk that might represent a state of the early Solar System. The dust does not seem to be a remnant from the original protoplanetary disk, but rather is thought to have been generated from large bodies like planetesimals and/or comets. The history and composition of the parent bodies can therefore be revealed by determining the spatial distribution, grain size, composition and crystallinity of the dust through high-resolution mid-infrared observations. Here we report that the sub-micrometre amorphous silicate grains around beta Pic have peaks in their distribution around 6, 16 and 30 au (1 au is the Sun-Earth distance), whereas the crystalline and micrometre-sized amorphous silicate grains are concentrated in the disk centre. As sub-micrometre grains are blown quickly out from the system by radiation pressure from the central star, the peaks indicate the locations of ongoing dust replenishment, which originates from ring-like distributions of planetesimals or 'planetesimal belts'.