Caffeine Junkie: an Unprecedented Glutathione S-Transferase-Dependent Oxygenase Required for Caffeine Degradation by Pseudomonas putida CBB5

Caffeine and other N-methylated xanthines are natural products found in many foods, beverages, and pharmaceuticals. Therefore, it is not surprising that bacteria have evolved to live on caffeine as a sole carbon and nitrogen source. The caffeine degradation pathway of Pseudomonas putida CBB5 utilizes an unprecedented glutathione-S-transferase-dependent Rieske oxygenase for demethylation of 7-methylxanthine to xanthine, the final step in caffeine N-demethylation. The gene coding this function is unusual, in that the iron-sulfur and non-heme iron domains that compose the normally functional Rieske oxygenase (RO) are encoded by separate proteins. The non-heme iron domain is located in the monooxygenase, ndmC, while the Rieske [2Fe-2S] domain is fused to the RO reductase gene, ndmD. This fusion, however, does not interfere with the interaction of the reductase with N₁- and N₃-demethylase RO oxygenases, which are involved in the initial reactions of caffeine degradation. We demonstrate that the N₇-demethylation reaction absolutely requires a unique, tightly bound protein complex composed of NdmC, NdmD, and NdmE, a novel glutathione-S-transferase (GST). NdmE is proposed to function as a noncatalytic subunit that serves a structural role in the complexation of the oxygenase (NdmC) and Rieske domains (NdmD). Genome analyses found this gene organization of a split RO and GST gene cluster to occur more broadly, implying a larger function for RO-GST protein partners.     

Mutation K42R in Ribosomal Protein S12 Does Not Affect Susceptibility of Mycobacterium smegmatis 16S rRNA A-Site Mutants to 2-Deoxystreptamines

Recent studies have suggested that ribosomal protein S12 modulates 16S rRNA function and susceptibility to 2-deoxystreptamine aminoglycosides. To study whether the non-restrictive K42R mutation in RpsL affects 2-deoxystreptamine susceptibility in Mycobacterium smegmatis, we studied the drug susceptibility pattern of various mutants with genetic alterations in the 16S rRNA decoding A-site in the context of wild-type and mutant protein S12. RpsL K42R substitution was found not to affect the drug resistance pattern associated with mutational alterations in 16S rRNA H44.     

Failure of duplexes based on polylaurusin [poly(L), “polyformycin B”] to induce interferon

Polylaurusin[poly(L) or “polyformycin B”] forms double-stranded complexes with polycytidylic acid (poly(C)) and with poly(5-bromocytidylic acid) [poly(br⁵C)] with T_m's of 46.5° (0.2 $\text{M}$ NaCl, pH 7) and 72.5° (0.15 M NaCl, pH 7), respectively. Both complexes fail to provide antiviral resistance (against vesicular stomatitis virus in primary rabbit kidney cells) or to induce interferon in “superinduced” primary rabbit kidney cells, even though they fulfill all previously recognized requirements for effective interferon inducers.     

Structure of the stridulation ofOrchelimum (Orthoptera: Tettigoniidae)

Summary The structure of the stridulation was investigated by re-playing tape-recordings at very slow speed. The findings were corrobrated by sonograms and mingograms.The central part of the song is the ripple, a fast succession of syllables around which isolated syllables (clicks) are distributed according to species and circumstances. The rate of syllables in the ripple is a linear function of temperature.A quantitative expression for the stridulatory activity is the actual number of syllables per time unit, including pauses. By changes in the combination of elements, at leastO. agile is able to increase the output of syllables four to six times.This work was made possible by a grant from the Carlsberg Foundation to whom my most sincere thanks are due. —As I do not have advanced equipment for sound analysis, I am very much indebted to Dr. Bondesen and cand. sci. Poul Hansen, Bioakustisk Laboratorium, Naturhistorisk Museum, Aarhus, Denmark, and Mr. W.B. Broughton and Dr. M. Samways, Animal Acoustic Unit, City of London Polytechnic, London, for analysing part of the material by sonograms and mingograms. The very valuable help of Dr. Th.J. Walker, University of Florida, Gainesville, Florida, in identifying the species is gratefully acknowledged. For friendly discussions and linguistic corrections my best thanks are due to H.T. Evans and F.D.S. Evans.     

Diversity,dynamics and reproduction in a community of small mammals in Upper Guinea,with emphasis on pygmy mice ecology

As part of a large survey on reservoirs of Lassa fever in Guinea, three villages were investigated in high endemic zone, close to Sierra Leone border. Biodiversity of the small mammal community is presented in this study through a standardized trapping in houses, cultivations and forest. Identification of the small mammals was based on morphology and by molecular technique for sibling species. Of the 1123 specimens collected in 2003–2005, we identified seventeen species (thirteen Muridae, four Soricidae), leading to high diversity (Shannon index = 1.6–1.8) and high equitability (evenness index = 0.7–0.8) in cultivations and forest. In houses conversely, the rodent community was dominated by Mastomys natalensis (95–98%), leading to low diversity and equitability. Dynamics and reproduction were investigated in two species of pygmy mice, Mus mattheyi and Mus minutoides, two species of Praomys, P. daltoni and P. rostratus, and in Mastomys erythroleucus. The pygmy mice were abundant in cultivations in early rainy season, and reproduced from rainy to dry season. Praomys daltoni was also found more abundant in cultivations and seemed to reproduce between rainy and dry season, whereas P. rostratus preferred forest and cultivations in late rainy season, and reproduced throughout the year. Finally, M. erythroleucus was more abundant in forest in dry season, and seemed to reproduce from late rainy to dry season. This species had a low occurrence (6.5%) in the Faranah’s zone, and probably lived at its southern limit in Guinea. The presence of other Murinae, such as M. natalensis, Praomys spp as possible competitors in the same habitats, is discussed. For the first time, this study relates population biology of pygmy mice with molecular identification.     

Translational issues for mitoprotective agents as adjunct to reperfusion therapy in patients with ST-segment elevation myocardial infarction

Pre-clinical studies have indicated that mitoprotective drugs may add cardioprotection beyond rapid revascularization, antiplatelet therapy and risk modification. We review the clinical efficacy of mitoprotective drugs that have progressed to clinical testing comprising cyclosporine A, KAI-9803, MTP131 and TRO 40303. Whereas cyclosporine may reduce infarct size in patients undergoing primary angioplasty as evaluated by release of myocardial ischaemic biomarkers and infarct size imaging, the other drugs were not capable of demonstrating this effect in the clinical setting. The absent effect leaves the role of the mitochondrial permeability transition pore for reperfusion injury in humans unanswered and indicates that targeting one single mechanism to provide mitoprotection may not be efficient. Moreover, the lack of effect may relate to favourable outcome with current optimal therapy, but conditions such as age, sex, diabetes, dyslipidaemia and concurrent medications may also alter mitochondrial function. However, as long as the molecular structure of the pore remains unknown and specific inhibitors of its opening are lacking, the mitochondrial permeability transition pore remains a target for alleviation of reperfusion injury. Nevertheless, taking conditions such as ageing, sex, comorbidities and co-medication into account may be of paramount importance during the design of pre-clinical and clinical studies testing mitoprotective drugs.