Non-Viral Deoxyribonucleoside Kinases——Diversity and Practical Use

Deoxyribonucleoside kinases(d NKs) phosphorylate deoxyribonucleosides to their corresponding monophosphate compounds. d Nks also phosphorylate deoxyribonucleoside analogues that are used in the treatment of cancer or viral infections. The study of the mammalian d NKs has therefore always been of great medical interest. However, during the last 20 years, research on d NKs has gone into nonmammalian organisms. In this review, we focus on non-viral d NKs, in particular their diversity and their practical applications. The diversity of this enzyme family in different organisms has proven to be valuable in studying the evolution of enzymes. Some of these newly discovered enzymes have been useful in numerous practical applications in medicine and biotechnology, and have contributed to our understanding of the structural basis of nucleoside and nucleoside analogue activation.     

Synthetic crowding agent dextran causes excluded volume interactions exclusively to tracer protein apoazurin

To understand protein biophysics in crowded cellular environments, researchers often use synthetic polymers as ‘crowding agents’ in vitro. The idea is that these agents will occupy space and reproduce the in vivo scenario in terms of excluded volume. However, recent work has challenged this concept and pointed out that attractive interactions between protein and crowding agent will provide an enthalpic contribution to the overall effect on protein thermodynamics. Here we use a typical synthetic crowding agent and a well-studied model protein to demonstrate in a window of 50 K that the presence of dextran 20 affects apoazurin by steric repulsion.     

Sex hormone levels and body hair growth in !Kung San and Kavango men from Namibia

The relation between hair growth and levels of sex hormones in serum and saliva was investigated in 256 !Kung San and Kavango men (ages 18 to 39 years) from Namibia/Southern Africa. Serum concentrations of total testosterone (Tser), 5α-dihydrotestosterone (DHT), and estradiol (E2) as well as the level of bioavailable non-SHBG-bound testosterone in the saliva (Tsal) were determined by radioimmunoassay. The distribution and density of scalp and facial hair as well as the development of terminal hair on the chest, abdomen, pubic area, arms, fingers, and legs were categorized using objective criteria. Covariance analyses revealed marked differences in the distribution of body hair in the San and the Negro sample. This is partly explained by a significant influence of androgen and estrogen levels on the growth of terminal hair. DHT and the ratio DHT/Tser are significantly positively related to midphalangeal hair growth and negatively to pubic hair development. Tsal, the bioavailable fraction of total testosterone, exerts a weak positive influence on the degree of arm and leg hair growth; the most significant positive effect on the growth of abdominal, arm, and leg hair in our samples is caused by E2. The ratio Tser/E2 correlates significantly negatively with the arm and leg hair development and the ratio DHT/E2 with the degree of abdominal, pubic, arm, and leg hair, whereas lower DHT concentrations occur in men with stronger hair development. © 1993 Wiley-Liss, Inc.     

Growth energetics of an alkaline serine protease-producing strain of Bacillus clausii during continuous cultivation

Glucose-limited chemostats were used to determine the growth yields of biomass of Bacillus clausii PP 473-8 producing an alkaline serine protease Savinase (Novozymes A/S, Bagsværd, Denmark) and a low yield of biomass on oxygen was observed. The energy metabolism was investigated further by setting up simple stoichiometric models for growth on glucose and citrate. In order to determine the parameters in the models, a macromolecular biomass composition was determined based on measured values of protein and RNA combined with literature data. From the macromolecular composition of the biomass the theoretical co-factor and building block requirements needed for biomass formation were calculated. Using the stoichiometric models and data for growth on glucose and citrate the amount of ATP needed for biomass synthesis was estimated to 42.0 mmol ATP/gDW, the P/O ratio to 0.68 and the ATP maintenance to 2.93 mmol ATP/gDW/h. From these values it is concluded that the high oxygen consumption compared with other Bacillus species is due to a low efficiency in respiration resulting in a low P/O ratio. Finally, the energetic parameters were estimated for different architectures of the respiratory chain.     

8-methoxycaffeine inhibition of Drosophila DNA topoisomerase II.

We have investigated the effect of 8-methoxycaffeine on the interaction between Drosophila DNA topoisomerase II and DNA. We have shown that 8-methoxycaffeine affected the enzyme strand-passing activity by inhibiting decatenation of kinetoplast DNA, and that it interfered with the breakage-reunion reaction by stabilizing a cleavable complex. Treatment of the cleavable complex with protein denaturant resulted in DNA breaks. High resolution mapping of the cleavage sites in the central spacer region of Tetrahymena rDNA revealed that, contrary to what was observed with clinically important DNA topoisomerase II inhibitors, 8-methoxycaffeine did not modify the cleavage pattern observed without the drug.