Functional analysis of helicase and three tandem HRDC domains of RecQ in Deinococcus radiodurans / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement: a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose function, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ (DRRecQ) to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal (HRDC) domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism.

Relationship between antibacterial activity of aloe and its anthaquinone compounds / 中国中药杂志

<p><b>OBJECTIVE</b>To investigate the relationship between the antibacterial activity of aloe and its contents of anthaquinone compounds, measure and compale antibacterial activities of aloin and aloe-emodin, and analyse the effect of glycoside on the antibacterial activity of aloin.</p><p><b>METHOD</b>The antibacterial activities of the extracts from the outer leaf of Aloe saponaria Haw, aloin and aloe-emodin against three Gram-negative and two Gram-positive bacteria were investigated with the method of agar diffusion. The antibacterial effect of aloin on E. coli was further studied with scanning electron microscopy.</p><p><b>RESULT</b>The antibacterial activities of aloe showed to be dependent on the dose of anthraquinone, aloin (1 g x L(-1)) exhibited higher antibacterial activity [inhibition diameter > (7. 1 +/- 0.15) mm] than Aloe-emodin (inhibition diameter < 5.0 mm), and aloin changed the morphology of E. coli and damaged the outer cell structrue.</p><p><b>CONCLUSION</b>Anthraquinone compounds are the active antibacterial components in aloe and aloin is the main active compound. The glycoside makes it easy for aloin to invade cells and enhances its activity.</p>