The structure and function of the replication terminator protein of Bacillus subtilis: identification of the 'winged helix' DNA-binding domain.

The replication terminator protein (RTP) of Bacillus subtilis impedes replication fork movement in a polar mode upon binding as two interacting dimers to each of the replication termini. The mode of interaction of RTP with the terminus DNA is of considerable mechanistic significance because the DNA-protein complex not only localizes the helicase-blocking activity to the terminus, but also generates functional asymmetry from structurally symmetric protein dimers. The functional asymmetry is manifested in the polar impedance of replication fork movement. Although the crystal structure of the apoprotein has been solved, hitherto there was no direct evidence as to which parts of RTP were in contact with the replication terminus. Here we have used a variety of approaches, including saturation mutagenesis, genetic selection for DNA-binding mutants, photo cross-linking, biochemical and functional characterizations of the mutant proteins, and X-ray crystallography, to identify the regions of RTP that are either in direct contact with or are located within 11 angstroms of the replication terminus. The data show that the unstructured N-terminal arm, the alpha3 helix and the beta2 strand are involved in DNA binding. The mapping of amino acids of RTP in contact with DNA, confirms a 'winged helix' DNA-binding motif.     

Integrity of the P-site is probed during maturation of the 60S ribosomal subunit

Eukaryotic ribosomes are preassembled in the nucleus and mature in the cytoplasm. Release of the antiassociation factor Tif6 by the translocase-like guanosine triphosphatase Efl1 is a critical late maturation step. In this paper, we show that a loop of Rpl10 that embraces the P-site transfer ribonucleic acid was required for release of Tif6, 90 Å away. Mutations in this P-site loop blocked 60S maturation but were suppressed by mutations in Tif6 or Efl1. Molecular dynamics simulations of the mutant Efl1 proteins suggest that they promote a conformation change in Efl1 equivalent to changes that elongation factor G and eEF2 undergo during translocation. These results identify molecular signaling from the P-site to Tif6 via Efl1, suggesting that the integrity of the P-site is interrogated during maturation. We propose that Efl1 promotes a functional check of the integrity of the 60S subunit before its first round of translation.     

4-(Aminoalkylamino)-3-benzimidazole-quinolinones as potent CHK-1 inhibitors

CHK-1 is one of the key enzymes regulating checkpoints in cellular growth cycles. Novel 4-(amino-alkylamino)-3-benzimidazole-quinolinones were prepared and assayed for their ability to inhibit CHK-1. These compounds are potent cell permeable CHK-1 inhibitors and showed synergistic effect with a DNA-damaging agent, camptothecin.     

Precopulatory choice for cues of material benefits in tree crickets

The relative importance of direct and indirect benefits modelsof mate choice is a central question in sexual selection, butseparating the two models is very difficult because high qualitymales often provide both better direct benefits and better genes.In tree crickets, Oecanthus nigricornis, females have the opportunityto gain both directly and indirectly from mate choice. Femaletree crickets exercise premating choice for large males, butthe model underlying this choice is unknown. In this study weexamine the proximate cues used by female tree crickets to rejectmales, and show that the ability of males to provide food isa central cue. In contrast, we find no evidence that the relativesize of mates is important in mate rejection. The fact thatthe major phenotypic cues of male quality are related to foodprovisioning suggests that the role of genetic benefits in shapingfemale preferences is limited by the extent to which food provisioningsignals genetic quality.     

Preferred males are not always good providers: female choice and male investment in tree crickets

Female tree crickets (Oecanthus nigricornis) prefer large malesbut do not receive larger glandular courtship gifts from thesemales. This finding is puzzling from both the male and femaleperspectives, because females should prefer males providingmore direct benefits, and because males who provide larger giftsachieve higher insemination success. We tested for differencesin the quality of male secretions and found that larger malesprovided more proteinaceous food gifts than did rivals, whichcould explain why they are preferred by females. The preferencein turn could cause depletion of food gift reserves in favoredmales, because natural remating rates are high and because evena single feeding bout negatively affects glandular stores. Mostintriguingly, we showed that preferred males can adaptivelydecrease the size of courtship food-gifts provided (in orderto conserve gifts for future mating events) when they perceivethat the probability of multiple future mating opportunitiesis high. Thus, the elevated mating rates of preferred males(both before and after a focal mating event) could account forthe small size of their courtship food-gifts.     

Circadian variations of the plasma proteins in the adult male rat under natural synchronisation (author's transl)]

Circadian rhythms of blood total proteins, albumin, alpha 1-, alpha 2-, beta- and gamma-globulins were documented in 80 Wistar SPF adult male rats, synchronized by natural light (06.00-18.00 h) and darkness (18.00-06.00 h) during the month of October 78. Blood was sampled at four fixed time points in the 24 h scale (i.e. 04.00, 10.00, 16.00 or 24.00 h). Total proteins, albumin, alpha 2- and gamma-globulins showed a statistically significant rhythm with a maximum at 04.00 h. The data obtained in anaesthetized rats under artificial synchronization and in man are compared, taking into account that the rat is a nocturnally active rodent. The present work partially confirms the hypotheses of previous chronopharmacological studies, thus e.g. curarizing substances have a mimimum activity when the protein plasma level, especially albumin, is the highest.