Structure and function of the ion channel model system annexin V

Pressure-response analysis of anesthetic gases xenon and nitrous oxide on urate oxidase: a crystallographic study

The remarkably safe anesthetics xenon (Xe) and, to lesser extent, nitrous oxide (N(2)O) possess neuroprotective properties in preclinical studies. To investigate the mechanisms of pharmacological action of these gases, which are still poorly known, we performed both crystallography under a large range of gas pressure and biochemical studies on urate oxidase, a prototype of globular gas-binding proteins whose activity is modulated by inert gases. We show that Xe and N(2)O bind to, compete for, and expand the volume of a hydrophobic cavity located just behind the active site of urate oxidase and further inhibit urate oxidase enzymatic activity. By demonstrating a significant relationship between the binding and biochemical effects of Xe and N(2)O, given alone or in combination, these data from structure to function highlight the mechanisms by which chemically and metabolically inert gases can alter protein function and produce their pharmacological effects. Interestingly, the effects of a Xe:N(2)O equimolar mixture were found to be equivalent to those of Xe alone, thereby suggesting that gas mixtures containing Xe and N(2)O could be an alternative and efficient neuroprotective strategy to Xe alone, whose widespread clinical use is limited due to the cost of production and availability of this gas.

Functional analysis of the human annexin A5 gene promoter: a downstream DNA element and an upstream long terminal repeat regulate transcription

Human annexin A5 is a ubiquitous protein implicated in diverse signal transduction processes associated with cell growth and differentiation, and its gene regulation is an important component of this function. Promoter transcriptional activity was determined for a wide 5' portion of the human annexin A5 gene, from bp -1275 to +79 relative to the most 5' of several discrete transcription start points. Transfection experiments carried out in HeLa cells identified the segment from bp -202 to +79 as the minimal promoter conferring optimal transcriptional activity. Two canonical Sp1 sites in the immediate 5' flanking region of a CpG island were required for significant transcription. Strong repressive activity in the distal promoter region between bp -717 to -1153 was attributed to the presence of an endogenous retroviral long terminal repeat, homologous with long terminal repeat 47B. The downstream sequence from bp position +31 to +79 in untranslated exon 1 was also essential for transcription, as its deletion from any of the plasmid constructs abolished activity in transfection assays. Electrophoretic mobility-shift assays, Southwestern-blot analysis and affinity chromatography were used to identify a protein doublet of relative molecular mass 35 kDa that bound an octanucleotide palindromic sequence in exon 1. The DNA cis-element resembled an E-box, but did not bind higher molecular mass transcription factors, such as upstream stimulatory factor or activator protein 4. The discovery of a downstream element crucial for annexin A5 gene transcription, and its interaction with a potentially novel transcription factor or complex, may provide a clue to understanding the initiation of transcription by TATA-less, multiple start site promoters.