Conservation biology. Galápagos station survives latest attack by fishers.

Researchers at the Darwin Research Station are attempting to put the pieces back together after a festering dispute over fishing quotas turned violent between 13 and 17 November. The fuse that set off the most recent conflagration was an annual 50-ton limit on spiny lobsters that local fishers reached barely halfway into the 4-month season. Unruly bands of fishers laid siege to the station and the park service, blocked roads and offices, tore down the island's telephone antenna, and destroyed research records.

Osteoporosis. Cholesterol drugs show promise as bone builders.

A group of drugs called statins that are used by millions to head off heart disease seem not only to prevent fractures, but they may also trigger significant bone regrowth, according to four studies reported in the 28 June issue of The Journal of the American Medical Association and the 24 June issue of The Lancet. And another promising treatment, a recombinant fragment of human parathyroid hormone called rhPTH, is even closer to the clinic: Two clinical trials reported at meetings in the past 2 weeks show that the compound builds bone and lowers the risk of fracture by more than half. These findings could be good news for the millions of people worldwide who suffer from osteoporosis.

Lipid research. Possible new way to lower cholesterol.

Clinicians may soon be able to mount a multipronged attack against cholesterol, the artery-clogging lipid whose buildup in the body is a major contributor to heart attacks and other cardiovascular diseases. In work reported on page 1524, a team has pinpointed a biological master switch in mice that controls three pathways that work together to both rid the body of excess cholesterol and prevent its absorption from the intestine. The work suggests a new mechanism for reducing cholesterol, for example, with drugs that turn up the activity of the master switch, a protein known as the retinoid X receptor.

Primatology. Human diseases threaten great apes.

Researchers are uncovering disturbing evidence that scientists and tourists are infecting wild primates with human pathogens. In response, ape specialists, including the American Society of Primatologists, are now calling for stricter health standards for researchers and tourists. They are also urging researchers to learn how to diagnose disease in their study animals.

Bradhyrhizobium japonicum hydrogen-ubiquinone oxidoreductase activity: quinone specificity, inhibition by quinone analogs, and evidence for separate sites of electron acceptor reactivity.

The purified H2-uptake hydrogenase of Bradyrhizobium japonicum, containing no cytochrome b, catalyzed efficient H2-ubiquinone oxidoreductase activity. Hydrogen-oxidizing membranes also catalyzed H2-ubiquinone oxidoreductase activity, and the site of ubiquinone reduction was localized to the He-quinone oxidoreductase complex based on comparative antimycin A and HQNO titrations of both H2-ubiquinone-1 oxidoreductase and ubiquinol-1 oxidase activities. A variety of quinones could function as electron acceptors of both pure or membrane-bound hydrogenase, including ubiquinone-0 (Q0), ubiquinone-1 (Q1), duroquinone and menadione, indicating relatively loose substrate specificity with regard to the quinone head group. Both the redox potential and the quinone structure determined the efficiency of hydrogenase turnover. Among short-chain ubiquinones, the isoprenoid chain length had a profound affect on Kin, with each additional isoprenoid unit resulting in the K m of the membrane-bound enzyme to decrease more than an order of magnitude. For pure enzyme, the K m values for Q0, Q1 and Q2 were 1.97 mM, 68.8 /xM and 3.1 /~M, respectively. Vma x was also influenced by the substrate isoprenoid chain length for the pure enzyme. The inhibition patterns of H2-dependent Q1 versus MB reduction by the quinone analogs (2-n-heptyl-4-hydroxyquinoline N-oxide and Antimycin A) were significantly different, and clear differences in pH optima for the two activities were observed. In addition, the two hydrogen-dependent electron acceptor activities (Q1 and MB) exhibited different time-dependent inactivation patterns by the chemical modification reagent diazobenzene sulfonate. Ubiquinone and MB therefore react by different mechanisms (perhaps at different sites) within the hydrogenase complex in situ. The inhibition pattern of hydrogen-ubiquinone oxidoreductase activity by antimycin A was clearly different than antimycin A inhibition of ubiquinol oxidation at the bc1 complex. This is, to our knowledge, the first report of antimycin A inhibition of a hydrogenase complex, and also of a quinone reducing site of a primary dehydrogenase. When pure hydrogenase is assayed in the absence of dithionite, a delay (lag phase) is observed prior to attainment of full activity. The length of this lag period (in minutes) was inversely dependent on ubiquinone concentration, and was greatly reduced (but not eliminated) at saturating ubiquinone levels. These effects were obtained with both Q1 and MB as electron acceptor, and the lag phases with Q1 were significantly longer than with MB. Electron acceptor binding to hydrogenase is thus required for reductive activation of hydrogenase during turnover.

The adenylate kinase genes of M. voltae, M. thermolithotrophicus, M. jannaschii, and M. igneus define a new family of adenylate kinases.

The adenylate kinase genes (adkA) were cloned from four closely related methanogenic members of the Archaea: the mesophile Methanococcus voltae (Mv), the thermophile M. thermolithotrophicus (Mt) and the hyperthermophiles M. jannaschii (Mj) and M. igneus (Mi). All four genes encode a protein of 192 amino acids (aa), and the four enzymes were closely related, with 68-81% aa identity in pairwise comparisons. It is anticipated that the enzyme set will provide the basis for studies that can establish the structural basis for ADK thermal stability. Mj and Mi contained a gene homologous to M. vannielii sec Y upstream of adkA, while Mv and Mt contained an unidentified, yet conserved, upstream open reading frame (ORF). Mt, Mj and Mi, but not Mv, contained an unidentified, yet highly conserved, ORF directly downstream of adkA. Based on their size, predicted secondary structure and phylogenetic relation to bacterial and eukaryotic adenylate kinases (ADK), it was concluded that the archaeal adkA genes encoded a unique class of ADK, and suggested that Euryarchaeotal and Crenarchaeotal branches of the Archaea contain separate subclasses of the enzyme.

Hydrogen-ubiquinone oxidoreductase activity by the Bradyrhizobium japonicum membrane-bound hydrogenase.

The Bradyrhizobium japonicum heterodimeric nickel-iron hydrogenase efficiently catalyzed H2-ubiquinone-1 oxidoreductase activity at rates up to 47% of the maximal rates obtained using the artificial electron acceptor methylene blue. Gel filtration chromatography and SDS-polyacrylamide gel electrophoresis experiments demonstrated that the purified enzyme was a heterodimer containing only the 65 kDa and 33 kDa subunits. Reduced minus oxidized absorption difference spectra demonstrated the absence of detectable cytochromes. The H2-ubiquinone-1 oxidoreductase activity of both the purified heterodimeric hydrogenase and membranes was significantly inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide and antimycin A, inhibitors known to act in the quinone region of electron transport chains. Our results are the first report of H2-ubiquinone oxidoreductase activity by a purified hydrogenase.