Acquirement and characterization of a carotenoid mutant (GM309) of <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis> 601

A green mutant was obtained among the chemically induced mutants of Rhodobacter sphaeroides 601 (RS601) and named GM309. A blue shift of 20 nm of the carotenoid absorption spectrum was found in the light-harvesting complex II (LH2) of GM309. Different from LH2 of RS601, it was found that the carotenoids in GM309-LH2 changed to be neurosporene by mutation. Neurosporene lacks a conjugate double bond, compared with the spheroidene in RS601-LH2 which has ten conjugate double bonds. As shown by absorption and circular dichroism spectroscopy, the overall structure of GM309-LH2 is little affected by this change. From fluorescence emission spectra, it is found that GM309-LH2 can transfer energy from carotenoids to Bchl-B850 without any change in efficiency. But the efficiency of energy transfer from B800 to B850 in GM309-LH2 is decreased to be 42% of that of the native. This work would provide a novel method to investigate the mechanism of excitation energy transfer in LH2.     

Activation of K+ channels: an essential pathway in programmed cell death

Cell apoptosis and proliferation are two counterparts in sharing the responsibility for maintaining normal tissue homeostasis. In recent years, the process of the programmed cell death has gained much interest because of its influence on malignant cell growth and other pathological states. Apoptosis is characterized by a distinct series of morphological and biochemical changes that result in cell shrinkage, DNA breakdown, and, ultimately, phagocytic death. Diverse external and internal stimuli trigger apoptosis, and enhanced K+ efflux has been shown to be an essential mediator of not only early apoptotic cell shrinkage, but also of downstream caspase activation and DNA fragmentation. The goal of this review is to discuss the role(s) played by K+ transport or flux across the plasma membrane in the regulation of the apoptotic volume decrease and apoptosis. Attention has also been paid to the role of inner mitochondrial membrane ion transport in the regulation of mitochondrial permeability and apoptosis. We provide specific examples of how deregulation of the apoptotic process contributes to pulmonary arterial medial hypertrophy, a major pathological feature in patients with pulmonary arterial hypertension. Finally, we discuss the targeting of K+ channels as a potential therapeutic tool in modulating apoptosis to maintain the balance between cell proliferation and cell death that is essential to the normal development and function of an organism.     

A unique set of 11,008 onion expressed sequence tags reveals expressed sequence and genomic differences between the monocot orders Asparagales and Poales

Enormous genomic resources have been developed for plants in the monocot order Poales; however, it is not clear how representative the Poales are for the monocots as a whole. The Asparagales are a monophyletic order sister to the lineage carrying the Poales and possess economically important plants such as asparagus, garlic, and onion. To assess the genomic differences between the Asparagales and Poales, we generated 11,008 unique ESTs from a normalized cDNA library of onion. Sequence analyses of these ESTs revealed microsatellite markers, single nucleotide polymorphisms, and homologs of transposable elements. Mean nucleotide similarity between rice and the Asparagales was 78% across coding regions. Expressed sequence and genomic comparisons revealed strong differences between the Asparagales and Poales for codon usage and mean GC content, GC distribution, and relative GC content at each codon position, indicating that genomic characteristics are not uniform across the monocots. The Asparagales were more similar to eudicots than to the Poales for these genomic characteristics.     

Optimized expression and refolding of human keratoepithelin in BL21 (DE3)

Keratoepithelin (KE) is an extracellular protein participating in cell adhesion and differentiation. Mutations of the KE gene (on 5q31 in humans) cause deposition of abnormal proteins (amyloid and non-amyloid) in corneal stroma and lead to several corneal dystrophies in humans. However, further studies on the KE protein have been limited by the intrinsic difficulty of purifying this protein. A high-expression plasmid containing human KE gene was constructed to generate recombinant KE proteins in Escherichia coli. The plasmid was transformed into E. coli BL21 (DE3) and the recombinant protein was expressed as an insoluble His-tagged fusion protein and purified by nickel chelation affinity chromatography under denaturing conditions. On average, 12 mg of purified KE was routinely obtained from 1L of culture media. The recombinant KE was refolded in arginine-containing dialysis solutions and the recovery of bioactive KE typically was approximately 70%. The procedures developed in this report should enable reproducible production of KE and related mutant proteins in large quantities and facilitate future studies on biochemical and biophysical properties of KE and the pathogenesis of related corneal dystrophies.     

Identification and characterization of a novel cross-link lesion in d(CpC) upon 365-nm irradiation in the presence of 2-methyl-1,4-naphthoquinone

We report the isolation and characterization for the first time of a cross-link lesion between two adjacent cytosines from the 2-methyl-1,4-naphthoquinone (menadione)-sensitized 365-nm irradiation of d(CpC). Electrospray ionization mass spectrometry (ESI-MS), tandem MS and ¹H NMR results indicate that the cross-link occurs between the C5 carbon atom of one cytosine and the N⁴ nitrogen atom of the other cytosine. Furthermore, we synthesized d(CpC) with a ¹⁵N being incorporated on the amino group of either of the two cytosines. We then irradiated the two ¹⁵N-labeled dinucleoside monophosphates, isolated the cross-link products and characterized them by MS and multi-stage tandem MS. The latter results established unambiguously that the N⁴ nitrogen atom of the 3′-nucleobase is involved in the covalent bond formation between the two cytosines. This, in combination with two-dimensional nuclear Overhauser effect spectroscopy (NOESY) results, demonstrates that the cross-link arises from the formation of a covalent bond between the C5 carbon atom of the 5′ cytosine and the N⁴ nitrogen atom of the 3′ cytosine. We also show that the solution pH has a significant effect on the formation of the cross-link lesion, which supports that the deprotonation at the exocyclic amino group of cytosine cation radical is essential for the formation of the cross-link lesion.     

Toxicity of <Emphasis Type="Italic">Bacillus sphaericus</Emphasis> LP1-G Against Susceptible and Resistant <Emphasis Type="Italic">Culex quinquefasciatus</Emphasis> and the Cloning of the Mosquitocidal Toxin Gene

Bacillus sphaericus LP1-G, belonging to flagellar serotype H3, has been found to have moderate toxicity against two resistant Culex quinquefasciatus colonies (RLCq1 and RLCq2) and the susceptible contrast (SLCq). With an aim of screening mosquitocidal acting factor, a partial genome library was prepared from a partial HindIII digest of the total DNA from Bacillus sphaericus LP1-G. Two thousand twenty Escherichia coli clones were screened for toxicity against susceptible SLCq, and a toxic clone, designated E-UL68, was chosen for further study. The recombinant E-UL68 performed toxicity against both susceptible and two resistant colonies, having the same level of toxicity as that of wide-type strain LP1-G. Sequence analysis revealed that the inserted fragment was composed of 3876 nucleotides and contained a complete gene, whose sequence was identical to that of the mtx gene from B. sphaericus SSII-1. Because the binary toxin produced during sporulation of strain LP1-G has no activity against the target mosquitoes, this indicates that the Mtx toxin or other active factors might perhaps be responsible for the toxicity of LP1-G against different colonies of mosquito larvae.Received: 7 October 2002 / Accepted: 4 November 2002     

Immunoglobulin treatment suppresses atherosclerosis in apolipoprotein E-deficient mice via the Fc portion

Atherosclerosis is associated with immune activation. Immunoglobulin is used for the treatment of immune-mediated diseases. The mechanisms and importance of the Fc portion of immunoglobulin upon experimental atherosclerosis in apolipoprotein E-deficient mice were examined. Experimental atherosclerosis was induced in mice fed a high-fat diet containing 0.3% cholesterol. Over 8, 12, and 16 wk, on alternate days, mice were treated with an intraperitoneal injection of either 1 g.kg-1.day-1 of human intact immunoglobulin or F(ab')2 fragments of human immunoglobulin. Fatty streak formation and fibrofatty plaques were markedly suppressed in mice that received intact immunoglobulin for 8, 12, and 16 wk. In contrast, atherosclerotic lesions were not ameliorated in mice that received F(ab')2 fragments. Immunohistochemical analysis revealed that macrophage accumulation in the fatty streak lesions was suppressed in mice received intact immunoglobulin but not in those that received F(ab')2 fragments. In addition, the cytotoxic activities of splenocytes from immunoglobulin-treated mice, but not from F(ab')2 fragment-treated mice, were significantly suppressed compared with those from human serum albumin-treated mice. Differences in lesion area did not correlate with any significant alterations in serum lipid levels. Immunoglobulin therapy markedly suppressed atherosclerosis due to Fc receptor-mediated anti-inflammatory and immunomodulating actions. The antiatherosclerotic effects of immunoglobulin may be related to the suppression of cytotoxic activity of atherogenic T cells and the reduction of macrophage accumulation in the lesions.