Kikuchi fujimoto disease and systemic lupus erythematosus--a rare association.

Kikuchi-Fujimoto disease is rarely associated with systemic lupus erythematosus (SLE). Kikuchi Fujimoto disease may precede, follow or coincide with the diagnosis of SLE. We report a case who was initially diagnosed as Kikuchi Fujimoto disease with SLE. She is presently in remission after treatment of SLE.

Wavelength shifts correlation between near infrared and ultraviolet regions of the LHII bacteriochlorophyll spectrum from Ectothiorhodospira sp.

Bacteriochlorophyll a has a maximum at 258 nm previously related to the ring E ester system interacting with the pi-system of the macrocycle. In this work, we compared the effect of lauryldimethylamine-N-oxide (LDAO) and alkaline pH on both the near infrared and the ultraviolet region of the LHII spectrum from Ectothiorhodospira sp. While LDAO induces only a shift of the 850 nm band arising from the Qy transition of the bacteriochlorophyll a, alkaline pH also causes a concomitant and reversible 10-nm shift from 258 to 248 nm. Both shifts have similar apparent pKs (12.3 and 12.6, respectively). Interestingly, the presence of NaCl reduces these pKs values to 11.4 and 11.7.

Probing the binding site of 800-nm bacteriochlorophyll in the membrane-linked LH2 protein of Rhodobacter capsulatus by local unfolding and chemical modification: evidence for the involvement of a betaHis20 residue.

The aim of this study was to investigate the function of betaHis20 in the spectral behavior of the 800-nm bacteriochlorophyll (Bchl) of the Rhodobacter capsulatus LH2 protein. In this context, the 800-nm Bchl of the membrane-linked LH2 was used as an intrinsic probe to follow the reversible, denaturant-elicited unfolding of the neighboring protein region. This band was reversibly shifted to approximately 770 nm by acidic pH, suggesting that the environment of the pigment, responsible for its native red shift, was significantly disturbed by the protonation of a chemical group. The reversible acid-induced blue shift was only observed in the presence of unfolding agents (urea and guanidinium chloride). Thus, dismantling of the protein structure facilitated exposure of the basic group to the medium. The acid-base titrations of the spectral shift indicated an apparent pK approximately 6.1, a value consistent with His imidazole being the protonatable group responsible for the acid-induced band shift. The pK values of free N-terminal amino groups are higher and not expected to be lowered by their local environment in the unfolded state of the protein. A similar blue shift of the 800-nm Bchl band was caused by the modifier diethyl pyrocarbonate, which is known to carboxylate the imidazole group of His and free amino groups. It is also shown that the Fourier transform Raman spectrum of diethyl pyrocarbonate-treated LH2 preparations lacks the weak mode at 1695 cm(-1), suggesting that it should be assigned to the B800 Bchl.

Alkaline denaturation of the light-harvesting complex II from the purple bacterium Ectothiorhodospira sp.: kinetic evidence of the existence of the 780 nm upper exciton component of the B850 bacteriochlorophylls.

The light-harvesting complex II of the purple bacteria has two strong near-infrared electronic absorption bands around 800 (B800) and 850 (B850) nm, arising from the Q(y)() transitions of the bacteriochlorophyll a. In the present work, high concentrations of NaOH were used to study the destabilization of the complex of the Ectothiorhodospira sp. The majority of the bacteriochlorophylls were monomerized within 90 min of treatment. However, the kinetic patterns of the two near-infrared bands were remarkably different. After an instantaneous blue shift from 853 to 828 nm, B850 showed a first-order monomerization with a rate constant of -0.016 min(-1). This instantaneous blue shift was previously attributed to the deprotonation of a lysine and was independent of the monomerization process. The observed native B800 is in fact composed of two bands, one at 796 nm and the other at 780 nm. The band absorbing at 780 nm red shifted also instantaneously to 786-788 nm and then disappeared in a first-order process as B850. The other band absorbing at 796 nm has a two-step process of monomerization; after a rapid conversion a slower first-order process occurred with a rate constant of -0.025 min(-1). The similarity between the kinetic behaviors of B850 and the 780 nm band indicated a strong relationship between these two bands. Our interpretation of the results considers the 780 nm band as the upper exciton component of the B850 bacteriochlorophylls.

Effects of acid pH and urea on the spectral properties of the LHII antenna complex from the photosynthetic bacterium Ectothiorhodospira sp.

The aim of this study was to investigate the spectral modifications of the LHII antenna complex from the purple bacterium Ectothiorhodospira sp. upon acid pH titration both in the presence and absence of urea. A blue shift specifically and reversibly affected the B850 band around pH 5.5-6.0 suggesting that a histidine residue most probably participated in the in vivo absorption red shifting mechanism. This transition was observed in the presence and absence of urea. Under strong chaotropic conditions, a second transition occurred around pH 2.0, affecting the B800 band irreversibly and the B850 reversibly. Under these conditions a blue shift from 856 to 842 nm occurred and a new and strong circular dichroism signal from the new 842 nm band was observed. Reverting to the original experimental conditions induced a red shift of the B850 band up to 856 nm but the circular dichroism signal remained mostly unaffected. Under the same experimental conditions, i.e. pH 2.1 in the presence of urea, part of the B800 band was irreversibly destroyed with concomitant appearance of a band around 770 nm due to monomeric bacteriochlorophyll from the disrupted B800. Furthermore, Gaussian deconvolution and second derivative of the reverted spectra at pH 8.0 after strong-acid treatment indicated that the new B850 band was actually composed of two bands centered at 843 and 858 nm. We ascribed the 858 nm band to bacteriochlorophylls that underwent reversible spectral shift and the 843 nm band to oligomeric bacteriopheophytin formed from a part of the B850 bacteriochlorophyll. This new oligomer would be responsible for the observed strong and mostly conservative circular dichroism signal. The presence of bacteriopheophytin in the reverted samples was definitively demonstrated by HPLC pigment analysis. The pheophytinization process progressed as the pH decreased below 2.1, and at a certain point (i.e. pH 1.5) all bacteriochlorophylls, including those from the B800 band, became converted to oligomeric bacteriopheophytin, as shown by the presence of a single absorption band around 843 nm and by the appearance of a single main elution peak in the HPLC chromatogram which corresponded to bacteriopheophytin.

A study on the heterogeneity of the light-harvesting complex II from Ectothiorhodospira sp. after acid/chaotropic treatment.

The light-harvesting complex II of the purple bacteria has two strong near infrared electronic absorption bands, around 800 (B800) and 850 (B850) nm, arising from the Qy transitions of bacteriochlorophyll a. It was previously reported that under some specific acid/chaotropic conditions the B850 bacteriochlorophylls of the light-harvesting complex II of Ectothiorhodospira sp. are strongly reorganised. Part of these pigments absorbs at 843 nm while another set absorbs around 858 nm. The current work should investigate whether a mix of two different complexes could generate the 843- and 858-nm bands. Acid/chaotropic conditions inducing the reorganisation of B850 were reproduced on a sample bound to an ionic-exchange column. The chromatographic pattern was found strongly homogeneous. The findings indicate that the heterogeneity of the reorganised B850 results from two forms of differently structured bacteriochlorophylls bound to the same polypeptide backbone.

Periplasmic electron carriers and photo-induced electron transfer in the photosynthetic bacterium Ectothiorhodospira sp.

A detailed analysis of the periplasmic electron carriers of the photosynthetic bacterium Ectothiorhodospira sp. has been performed. Two low mid-point redox potential electron carriers, cytochrome c' and cytochrome c, are detected. A high potential iron-sulfur protein is the only high mid-point redox potential electron transfer component present in the periplasm. Analysis of light-induced absorption changes shows that this high potential iron-sulfur protein acts in vivo as efficient electron donor to the photo-oxidized high potential heme of the Ectothiorhodospira sp. reaction center.

Interaction between ATP, oleandomycin and the OleB ATP-binding cassette transporter of Streptomyces antibioticus involved in oleandomycin secretion.

The OleB protein of Streptomyces antibioticus, oleandomycin (OM) producer, constitutes an ATP-binding cassette transporter containing two nucleotide-binding domains and is involved in OM resistance and its secretion in this producer strain. We have characterized some properties of the first nucleotide-binding domain of OleB using an overexpressed fusion protein (MBP-OleB') between a maltose-binding protein (MBP) and the first half of OleB (OleB'). Extrinsic fluorescence of the base-modified fluorescent nucleotide analogue 1,N6-ethenoadenosine 5'-triphosphate (epsilon ATP) and 2'(3')-o-(2,4,6-trinitrophenyl)adenosine-5'-triphosphate was determined in the presence of MBP and the fusion protein MBP-OleB', and it was found that epsilon ATP binds to MBP-OleB' with a stoichiometry of 0.9. Measurements of the intrinsic fluorescence of the MBP-OleB' fusion protein indicated that ATP induces a decrease in the accessibility of the MBP-OleB' tryptophans to acrylamide, an indication of a folding effect. This conclusion was confirmed by the fact that ATP also induces considerable stabilization against guanidine chloride denaturation of MBP-OleB'. Two effects were found to be associated with the presence of Mg2+ ions: (1) an increase in the quenching of MBP-OleB' intrinsic fluorescence by ATP; and (2) an increase in the accessibility of MBP-OleB' tryptophans to acrylamide. Significant changes in the intrinsic fluorescence of the fusion protein were also observed in the presence of OM, demonstrating the existence of interaction between the transporter and the antibiotic in the absence of any hydrophobic membrane component.

Characterization of the ATPase activity of the N-terminal nucleotide binding domain of an ABC transporter involved in oleandomycin secretion by Streptomyces antibioticus.

The oleB gene of Streptomyces antibioticus, oleandomycin producer, encodes an ABC transporter containing two putative ATP-binding domains and is involved in oleandomycin resistance and secretion in this organism. We have overexpressed in Escherichia coli the N-terminal nucleotide-binding domain of OleB (OleB') as a fusion protein and purified the fusion protein by affinity chromatography. The fusion protein showed ATPase activity dependent on the presence of Mg2+ ions. ATPase activity was resistant to specific inhibitors of P-, F-, and V-type ATPase whereas sodium azide and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-C1) were strong inhibitors. The change of Lys71, located within the Walker A motif of the OleB' protein, to Gln or Glu caused a loss of ATPase activity, whereas changing to Gly did not impair the activity. The results suggest that the intrinsic ATPase activity of purified fusion protein can be clearly distinguished from other ATP-hydrolysing enzymes, including ion-translocating ATPases or ABC-traffic ATPases, both on the basis of inhibition by different agents and since it hydrolyzes ATP without interacting with a hydrophobic membrane component.

Tolerance to osmotic shocks in rats kidney cortex and medulla.

Kidney medulla cells of mammals have to cope with large changes in environmental osmolarity, a challenge most other mammalian cells never have to experience. In these last cells, application of osmotic shocks induces dramatic modifications in chromatin organization. The present paper reports on the changes of medulla cell chromatin in situ, in rat kidney slices submitted to osmotic challenges and in vitro, on preparations of extracted chromatin submitted to changes in environmental ion concentrations. Our results show that the chromatin of kidney medulla cells: (1) does not behave differently from the other mammalian chromatins when submitted in situ or in vitro to osmotic challenges; (2) presents in vitro physico-chemical characteristics similar to those of the other mammalian chromatins; and (3) is protected in vitro, as the other mammalian chromatins, from the disrupting effects of increases in inorganic ion concentrations by different compensatory organic solutes. The ability of kidney medulla cells to adapt to large increases in osmolarity could thus be related to a rapid control of the level of such compounds rather than to some rather specific, intrinsic molecular adaptations of macromolecules.

Effect of organic effectors on chromatin solubility, DNA-histone H1 interactions, DNA and histone H1 structures.

We have extended our previous investigations on the effect of organic osmolytes (glycine, proline, taurine, mannitol, sorbitol and trimethylammonium oxide (TMAO)) on chromatin solubility, to the study of their influence on DNA stability and DNA-histone interactions. Our aim was to understand the molecular origin of the protection effects observed. To this end, we determined the amount of histone H1 required to precipitate DNA or H1-depleted chromatin, at various salt concentrations, in the presence of the above mentioned organic compounds. We found a shift of the H1/DNA ratio required to reach 50% precipitation, towards higher values. Taurine was the most efficient compound followed by mannitol and glycine, then sorbitol and proline. On the contrary, TMAO favoured the precipitation process. We attempted to interpret these results on the basis of Manning's counterion condensation theory. Changes in histone H1 structure folding and in DNA melting temperature Tm were also analyzed. Glycine, taurine, sorbitol and TMAO increased the degree of secondary structure folding of the protein while mannitol and sorbitol had no effect. Taurine, glycine and proline decreased the Tm of DNA, TMAO largely destabilized DNA, but mannitol and sorbitol had no effect. Measurements of NaCl activity in the presence of organic osmolytes did not reveal sufficiently large changes to account for their protection effect against chromatin precipitation. The osmotic coefficient j of the organic effectors solutions increased in the order: taurine < glycine < sorbitol < mannitol < proline << TMAO. For the two latter compounds, the j values increased above 1 at high concentration. We consider that the organic compounds investigated may be classified into three categories: (i) class I (zwitterionic compounds: glycine, proline, taurine) would produce sodium ions release from the DNA surface; (ii) class II (the very polar molecule TMAO) would increase sodium counterions condensation on DNA together with histone H1 folding; (iii) class III compounds (mannitol and sorbitol) would possibly produce a modification of NaCl activity but no definite explanation could be found for the complex behavior of these compounds.

Organic osmotic effectors and chromatin structure.

Organic amino compounds (taurine, glycine) and polyols (mannitol, sorbitol) are used as osmotic effectors by most animal cells, particularly by some marine invertebrates, but also to a limit extent by mammalian cells. Using physico-chemical techniques (circular dichroism, thermal denaturation, solubility, electrophoresis and electric linear dichroism), we demonstrated that some of these effectors prevent chromatin aggregation, without histone release. The influence of glycine on chromatin aggregation, dissociation and reconstitution was thoroughly investigated. Glycine at 2 M concentration does not in itself induce chromatin dissociation; it does hinder salt-induced histone dissociation from chromatin (especially at 1.2 M NaCl) but does not impede chromatin reconstitution. Several hypothesis may be put forward to explain the action of these effectors: (i) a modulation of histone conformation; (ii) a modification of fractional DNA charge, either directly by the zwitterions (glycine, taurine) or indirectly by alteration of cations counterions hydration. The physiological relevance of our experiments is also discussed.

Glycine and other amino compounds prevent chromatin precipitation at physiological ionic strength.

Glycine, proline and taurine, when present in the range 0.1-0.60 M, inhibit chromatin precipitation by sodium chloride. Histone gel electrophoresis revealed that the linker histones H1 and H5 were largely depleted from the supernatant chromatin fraction at 0.2 M NaCl, while this depletion was absent in the presence of glycine. These observations are discussed in relation with the various factors which may be involved in the precipitation process.