Methoxymercuration-demercuration and mass spectrometry in the identification of the sex pheromones ofPanolis flammea,the pine beauty moth

Summary The major components of the sex pheromone system ofPanolis flammea, pine beauty moth have been identified as (Z)-9-tetradecenyl acetate, (Z)-11-hexadecenyl acetate and (Z)-11-tetradecenyl acetate in the ratio 10051; the double bond position of these derivatives was established by microscale application of a methoxymercuration-demercuration technique and GC-MS followed by multiple ion monitoring.We thank the Science Research Council and Forestry Commission for financial support. We are grateful for the collaboration of Messrs Stoakley and Bevan, Dr C. Longhurst and Mrs J. Edwards.     

A 42K outer-membrane protein is a component of the yeast mitochondrial protein import site

An engineered precursor protein that sticks in the import site of isolated yeast mitochondria can be specifically photo-crosslinked to a mitochondrial outer-membrane protein of relative molecular mass 42,000 (42K). This protein (termed import-site protein 42 or ISP 42) is exposed on the mitochondrial surface; antibodies against it block protein import into mitochondria. ISP 42 is the first identified component of the putative transmembrane machinery that imports proteins into mitochondria.     

Mitotic regulation of the anaphase-promoting complex

Orderly progression through mitosis is regulated by the anaphase-promoting complex/cyclosome (APC/C), a large multiprotein E3 ubiquitin ligase that targets key mitotic regulators for destruction by the proteasome. APC/C has two activating subunits, Cdc20 and Cdh1. The well-established view is that Cdc20 activates APC/C from the onset of mitosis through the metaphase-anaphase transition, and that Cdh1 does so from anaphase through G1. Recent work, however, indicates that Cdh1 also activates APC/C in early mitosis and that this APC/C pool targets the anaphase inhibitor securin. To prevent premature degradation of securin, the nuclear transport factors Nup98 and Rae1 associate with APC/C^Cdh1-securin complexes. In late metaphase, when all kinetochores are attached to spindle microtubules and the spindle assembly checkpoint is satisfied, Nup98 and Rae1 are released from these complexes, thereby allowing for prompt ubiquitination of securin by APC/C^Cdh1. This, and other mechanisms by which the catalytic activity of APC/C is tightly regulated to ensure proper timing of degradation of each of its mitotic substrates, are highlighted. Received 8 October 2006; received after revision 24 November 2006; accepted 8 January 2007     

A protein-folding reaction under kinetic control.

Synthesis of alpha-lytic protease is as a precursor containing a 166 amino-acid pro region transiently required for the correct folding of the protease domain. By omitting the pro region in an in vitro refolding reaction we trapped an inactive, but folding competent state (I) having an expanded radius yet native-like secondary structure. The I state is stable for weeks at physiological pH in the absence of denaturant, but rapidly folds to the active, native state on addition of the pro region as a separate polypeptide chain. The mechanism of action of the pro region is distinct from that of the chaperonins: rather than reducing the rate of off-pathway reactions, the pro region accelerates the rate-limiting step on the folding pathway by more than 10(7). Because both the I and native states are stable under identical conditions with no detectable interconversion, the folding of alpha-lytic protease must be under kinetic and not thermodynamic control.     

Sex pheromone communication in the lepidoptera: New research progress

Summary Significant progress has been made recently in research on lepidopterous sex pheromones. Advances in understanding the biochemical, neurobiological, and behavioral events that results in both successful and unsuccessful pheromone communication have allowed researchers to gain new insights into the genetic control and evolution of phermone systems.     

Imaging of Titan from the Cassini spacecraft

Titan, the largest moon of Saturn, is the only satellite in the Solar System with a substantial atmosphere. The atmosphere is poorly understood and obscures the surface, leading to intense speculation about Titan's nature. Here we present observations of Titan from the imaging science experiment onboard the Cassini spacecraft that address some of these issues. The images reveal intricate surface albedo features that suggest aeolian, tectonic and fluvial processes; they also show a few circular features that could be impact structures. These observations imply that substantial surface modification has occurred over Titan's history. We have not directly detected liquids on the surface to date. Convective clouds are found to be common near the south pole, and the motion of mid-latitude clouds consistently indicates eastward winds, from which we infer that the troposphere is rotating faster than the surface. A detached haze at an altitude of 500 km is 150-200 km higher than that observed by Voyager, and more tenuous haze layers are also resolved.     

Early planetesimal melting from an age of 4.5662 Gyr for differentiated meteorites

Long- and short-lived radioactive isotopes and their daughter products in meteorites are chronometers that can test models for Solar System formation. Differentiated meteorites come from parent bodies that were once molten and separated into metal cores and silicate mantles. Mineral ages for these meteorites, however, are typically younger than age constraints for planetesimal differentiation. Such young ages indicate that the energy required to melt their parent bodies could not have come from the most likely heat source-radioactive decay of short-lived nuclides ((26)Al and (60)Fe) injected from a nearby supernova-because these would have largely decayed by the time of melting. Here we report an age of 4.5662 +/- 0.0001 billion years (based on Pb-Pb dating) for basaltic angrites, which is only 1 Myr younger than the currently accepted minimum age of the Solar System and corresponds to a time when (26)Al and (60)Fe decay could have triggered planetesimal melting. Small (26)Mg excesses in bulk angrite samples confirm that (26)Al decay contributed to the melting of their parent body. These results indicate that the accretion of differentiated planetesimals pre-dated that of undifferentiated planetesimals, and reveals the minimum Solar System age to be 4.5695 +/- 0.0002 billion years.     

Development of Th1-type immune responses requires the type I cytokine receptor TCCR

On antigen challenge, T-helper cells differentiate into two functionally distinct subsets, Th1 and Th2, characterized by the different effector cytokines that they secrete. Th1 cells produce interleukin (IL)-2, interferon-gamma (IFN-gamma) and lymphotoxin-beta, which mediate pro-inflammatory functions critical for the development of cell-mediated immune responses, whereas Th2 cells secrete cytokines such as IL-4, IL-5 and IL-10 that enhance humoral immunity. This process of T-helper cell differentiation is tightly regulated by cytokines. Here we report a new member of the type I cytokine receptor family, designated T-cell cytokine receptor (TCCR). When challenged in vivo with protein antigen, TCCR-deficient mice had impaired Th1 response as measured by IFN-gamma production. TCCR-deficient mice also had increased susceptibility to infection with an intracellular pathogen, Listeria monocytogenes. In addition, levels of antigen-specific immunoglobulin-gamma2a, which are dependent on Th1 cells, were markedly reduced in these mice. Our results demonstrate the existence of a new cytokine receptor involved in regulating the adaptive immune response and critical to the generation of a Th1 response.     

A surprising simplicity to protein folding

The polypeptide chains that make up proteins have thousands of atoms and hence millions of possible inter-atomic interactions. It might be supposed that the resulting complexity would make prediction of protein structure and protein-folding mechanisms nearly impossible. But the fundamental physics underlying folding may be much simpler than this complexity would lead us to expect folding rates and mechanisms appear to be largely determined by the topology of the native (folded) state, and new methods have shown great promise in predicting protein-folding mechanisms and the three-dimensional structures of proteins.