[Study on protective effects and mechanisms of total glucosides of Paeony on Graves disease in BALB/c mice]

Objective: To investigate the protective effect and its immunoregulatory mechanism of Total Glucosides of Paeony (TGP) against Graves' Disease (GD) model on BALB/c mice. Methods: Fifty female (6 weeks old, weighing 16-18 g) BALB/c mice of specific pathogen free were divided into control group according to random number table method, model group, early low-dose TGP intervention group (250 mg·kg^-1·d^-1), early high-dose TGP intervention group (500 mg·kg^-1·d^-1), and late TGP intervention group, with 10 mice in each group. Except the control group, the other 4 groups were immunized 3 times (0, 3^rd, and 6^th week) with recombinant adenovirus expressing the thyroid stimulating hormone receptor (TSHR) A subunit to establish the GD model. The early low-dose and high-dose intervention group were given diets containing different doses of TGP throughout the whole process, and the late intervention group was given diets containing low doses of TGP from the 1^st week after the 2^nd immunization (week 4). The levels of thyrotropin receptor antibody (TRAb) and total thyroxine (TT4) were detected in the tail venous blood of mice at the 4^th week. At the 10^th week, the serum TRAb and TT4 levels and the ratio of regulatory T cells (Treg) in each group were detected, and the pathological changes of thyroid tissue were observed. Serum helper T cell 1(Th1) and Th2 cell-related factors interleukin-2 (IL-2), IL-4, IL-5, IL-10, IL-12p70, granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-γ (IFN-γ) and tumor necrosis factors-α (TNF-α) were detected to investigate the protective effect of TGP on GD model in BALB/c mice and its mechanism. Results: At the 4^th week, The level of TT4 [(55.07±12.89) μg/L] in early high-dose intervention group was lower than that in model group [(74.33±8.63) μg/L] (all P<0.05). The level of TT4 in early low-dose intervention group and late intervention group and model group had no statistical significance (all P>0.05). TRAb level of mice between early low-dose, early high-dose, late intervention groups and model group was no significant difference (all P>0.05). At the 10^th week, TRAb [(90.00±26.89) U/L] and TT4[(32.66±8.11) μg/L] levels in the early high-dose intervention group were lower than those in the model group [(396.97±95.35) U/L, (73.70±16.33) μg/L] (all P<0.05). The TRAb and TT4 levels in the early low-dose intervention group and late intervention group were not significantly different from those in the model group (all P>0.05). The thyroid tissue of hyperthyroidism mice in the early high dose intervention group showed focal hypertrophic changes, while the thyroid tissue of other hyperthyroidism mice showed diffuse hypertrophic changes. The CD4⁺CD25⁺/CD4⁺Treg ratio in early high-dose intervention group was higher than that in model group at the 10^th week (4 weeks after three recombinant adenovirus immunization) (P<0.05). Compared with the model group at the 10^th week, the levels of IL-2, IL-12p70 and IFN-γ in the early high-dose intervention group were all decreased (all P<0.05), and the levels of IL-10 were increased (P<0.05). Conclusion: Early high-dose (500 mg·kg^-1·d^-1) TGP intervention group displays a protective effect against GD mice, the mechanism of which may be related to regulatory T cell function changes and Th1/Th2 cytokine balance restoration.

Assembly of Ultralong Hydroxyapatite Nanowires into Enamel-like Materials

To develop dental restorative materials with enamel-like structures, ultralong hydroxyapatite (HA) nanowires were synthesized by a hydrothermal method, followed by functionalization with 3-methacryloxypropyltrimethoxysilane (KH-570). The mixture of HA nanowires, KH-570, and light initiator was stirred and centrifuged. The precipitate was vacuum filtered to remove excessive KH-570 and then pressured under cold isostatic pressing (10 MPa × 24 h). Finally, the block was polymerized by lighting. Scanning electron microscopy and transmission electron microscopy showed that HA nanowires with aspect ratios >1,000 were assembled into enamel rod-like microstructures and evenly dispersed in the polymerized KH-570 silane matrix to form enamel-like structures. Thermogravimetric analysis demonstrated that the content of HA nanowires reached 72 wt% in the composite. The enamel-like composite showed a similar hardness, frictional property, and acid-etching property to those of enamel and a comparable or even better diametral tensile strength and compressive strength than some commercial composite resins in mechanical tests in vitro. In addition, the enamel-like composite had good cytocompatibility. Such enamel-like composites may have the potential to be used in biomimetic tooth restorations in the future.

[The influence of dihydrotestosterone on cytokine releases in male mice model with Graves disease]

Objective: To study the influences of dihydrotestosterone (DHT) on the development of experimental autoimmune Graves disease (EAGD), and to observe the effect of DHT on cytokines in male BALB/c mice model. Methods: Male BALB/c mice aged 6-8 weeks were divided into 4 groups using random number table: (1) control group; (2) EAGD group; (3) placebo group; (4) DHT group. EAGD mice were induced with an adenovirus expressing the human thyroid stimulating hormone receptor antibody A-subunit (Ad-TSHR289). DHT (5mg) or a matching placebo were implanted one week before the first immunization. Thyroid hormones were detected with radioimmunoassay kit.. Cytokines [such as interferonγ (IFNγ), interleukin (IL)-4, IL-10, IL-9, and IL-17] producing cells from the spleen were detected using flow cytometry. Results: As expected Ad-TSHR289 treatment increased total thyroxine [EAGD group vs. control group: (117.76±32.69) nmol/L vs. (33.08±12.61) nmol/L, P<0.0001] and free thyroxine [EAGD group vs. control group: (15.01±11.55) pmol/L vs. (3.55±1.88) pmol/L, P<0.0001]. Treatment of DHT slightly lowered thyroid hormones [DHT group vs. placebo group: total thyroxine (114.80±44.27) nmol/L vs. (123.17±77.73) nmol/L; free thyroxine (13.48±6.01) pmol/L vs. (14.19±12.65) pmol/L], without significant difference (all P>0.05)]. However, the percentage of IL-10, but not IFN γ, IL-4, IL-9 and IL-17, secreted spleen cells increased in DHT group than in the placebo group [(7.11±3.29)% vs. (3.51±1.36)%, P<0.05]. Conclusion: The effects of DHT on thyroid hormone are mild. It might play an immunomodulatory role in the male mouse Graves disease model by up-regulating the cytokine IL-10.

Complete genomic sequence of tea-oil camellia deltapartitivirus 1, a novel virus from Camellia oleifera

Three viral contig sequences, which represented complete genome of a novel virus with three dsRNAs of 1,712 nucleotides (nt) (dsRNA1), 1,504 nt (dsRNA2) and 1,353 nt (dsRNA3), were found in tea-oil camellia plants by high-throughput sequencing analysis. The three dsRNAs were re-sequenced by RT-PCR cloning. The largest dsRNA, dsRNA1, had a single open reading frame (ORF) that encoded a putative 52.7-kDa protein of a putative viral RNA-dependent RNA polymerase (RdRp). DsRNA2 and dsRNA3 were predicted to encode putative capsid proteins (CPs) of 40.47 kDa and 40.59 kDa, respectively. The virus, which is provisionally named "tea-oil camellia deltapartitivirus 1",  shared amino acid sequence itentities of 36.09-69.18% with members of the genus Deltapartitivirus on RdRp. Phylogenetic analysis based on RdRp also placed the new virus and other deltapartitiviruses together in a group, suggesting that this virus should be considered a new member of the genus Deltapartitivirus.

Molecular characterization and detection of two carlaviruses infecting cactus

Two large contigs with sequence similarities to different carlaviruses were identified by high-throughput sequencing in samples from a cactus plant. The complete genomes of the two viruses, tentatively named "cactus carlavirus 1" (CCV-1) and "cactus carlavirus 2" (CCV-2), were determined to be 8,441 and 8,396 nucleotides long, respectively, excluding the poly(A) tail. These viruses have the typical genomic organization of members of the genus Carlavirus. CCV-1 appears to be a cactus isolate of the carlavirus HSO-2016a, with 90.1% nucleotide sequence identity between the two virus genomes, whereas CCV-2 may be classified as a member of a new species. The sequences of CCV-2 and other carlaviruses are 48.9-60.0% identical at the whole-genome level.

Molecular characterization of a novel luteovirus from peach identified by high-throughput sequencing

Contigs with sequence homologies to cherry-associated luteovirus were identified by high-throughput sequencing analysis in two peach accessions. Complete genomic sequences of the two isolates of this virus were determined to be 5,819 and 5,814 nucleotides long, respectively. The genome of the new virus is typical of luteoviruses, containing eight open reading frames in a very similar arrangement. Its genomic sequence is 58-74% identical to those of other members of the genus Luteovirus. These sequences thus belong to a new virus, which we have named "peach-associated luteovirus".

Peptide and nucleic acid-directed self-assembly of cationic nanovehicles through giant unilamellar vesicle modification: Targetable nanocomplexes for in vivo nucleic acid delivery

One of the greatest challenges for the development of genetic therapies is the efficient targeted delivery of therapeutic nucleic acids. Towards this goal, we have introduced a new engineering initiative in self-assembly of biologically safe and stable nanovesicle complexes (∼90 to 140nm) derived from giant unilamellar vesicle (GUV) precursors and comprising plasmid DNA or siRNA and targeting peptide ligands. The biological performance of the engineered nanovesicle complexes were studied both in vitro and in vivo and compared with cationic liposome-based lipopolyplexes. Compared with cationic lipopolyplexes, nanovesicle complexes did not show advantages in transfection and cell uptake. However, nanovesicle complexes neither displayed significant cytotoxicity nor activated the complement system, which are advantageous for intravenous injection and tumour therapy. On intravenous administration into a neuroblastoma xenograft mouse model, nanovesicle complexes were found to distribute throughout the tumour interstitium, thus providing an alternative safer approach for future development of tumour-specific therapeutic nucleic acid interventions. On oropharyngeal instillation, nanovesicle complexes displayed better transfection efficiency than cationic lipopolyplexes. The technological advantages of nanovesicle complexes, originating from GUVs, over traditional cationic liposome-based lipopolyplexes are discussed.

STATEMENT OF SIGNIFICANCE

The efficient targeted delivery of nucleic acids in vivo provides some of the greatest challenges to the development of genetic therapies. Giant unilamellar lipid vesicles (GUVs) have been used mainly as cell and tissue mimics and are instrumental in studying lipid bilayers and interactions. Here, the GUVs have been modified into smaller nanovesicles. We have then developed novel nanovesicle complexes comprising self-assembling mixtures of the nanovesicles, plasmid DNA or siRNA, and targeting peptide ligands. Their biophysical properties were studied and their transfection efficiency was investigated. They transfected cells efficiently without any associated cytotoxicity and with targeting specificity, and in vivo they resulted in very high and tumour-specific uptake and in addition, efficiently transfected the lung. The peptide-targeted nanovesicle complexes allow for the specific targeted enhancement of nucleic acid delivery with improved biosafety over liposomal formulations and represent a promising tool to improve our arsenal of safe, non-viral vectors to deliver therapeutic cargos in a variety of disorders.

Hyperthyroid monkeys: a nonhuman primate model of experimental Graves' disease

Graves' disease (GD) is a common organ-specific autoimmune disease with the prevalence between 0.5 and 2% in women. Several lines of evidence indicate that the shed A-subunit rather than the full-length thyrotropin receptor (TSHR) is the autoantigen that triggers autoimmunity and leads to hyperthyroidism. We have for the first time induced GD in female rhesus monkeys, which exhibit greater similarity to patients with GD than previous rodent models. After final immunization, the monkeys injected with adenovirus expressing the A-subunit of TSHR (A-sub-Ad) showed some characteristics of GD. When compared with controls, all the test monkeys had significantly higher TSHR antibody levels, half of them had increased total thyroxine (T₄) and free T₄, and 50% developed goiter. To better understand the underlying mechanisms, quantitative studies on subpopulations of CD4+T helper cells were carried out. The data indicated that this GD model involved a mixed Th1 and Th2 response. Declined Treg proportions and increased Th17:Treg ratio are also observed. Our rhesus monkey model successfully mimicked GD in humans in many aspects. It would be a useful tool for furthering our understanding of the pathogenesis of GD and would potentially shorten the distance toward the prevention and treatment of this disease in human.

Involvement of nuclear factor κB (NF-κB) in the downregulation of cyclooxygenase-2 (COX-2) by genistein in gastric cancer cells

Genistein induces growth inhibition in various human cancer cell lines but its mechanism of action remains unknown. This study determined whether the effect of genistein is mediated via suppression of cyclo-oxygenase (COX)-2 protein, and elucidated the mechanism of action of this effect in the human gastric cancer cell line BGC-823. Genistein treatment inhibited cell proliferation and induced apoptosis in a dose- and time-dependent manner; Western blotting analysis indicated a significant dose-dependent decrease in COX-2 protein levels. Genistein treatment exerted a significant inhibitory effect on activation of the transcription factor nuclear factor κB (NF-κB). Additionally, the NF-κB inhibitor pyrrolidine dithiocarbamate caused a reduction in COX-2 protein levels and NF-κB activation, similar to the effect of genistein. Suppression of COX-2 protein may be important for the antiproliferative and proapoptotic effects of genistein in BGC-823 cells, and these effects may be partly mediated through the NF-κB pathway.

Community health information and its management system: a new form for the next century

The development of community health service brings a new branch of Medical Informatics, Community health care informatics and a new management system, Community Health Care Information System in the beginning of nest century. The paper first advance and explore this new concept. It states the focus of Community health care informatics as the promotion of health for the whole community. It not only gives treatment to individual patients through ways of disease management and information network, but also improves health condition of the whole community by "diagnosis of community health" and "prescription for community health". The paper also introduces the community health information system and its formation, technology, function and practical use, pointing out the crucial point of its research work to be precisely discovering the "information origin" and "three-in-one" working group.

[Studies of hypoxic rat brain mitochondrial transcription activity in vitro]

AIM

To explore the effects of acute and chronic hypoxia on brain mitochondrial transcription activity in vitro of rats.

METHODS

Animal grouping: Wistar rats were randomized into acute hypoxic group (AH), chronic hypoxic group (CH) and the control. Mitochondrial transcription activity in vitro was measured in each group respectively as well as mitochondrial F0F1-ATPase activity, and effects of environmental ATP concentration on mitochondrial transcription activity in vitro was observed.

RESULTS

Brain mitochondrial transcription activity and F0F1-ATPase activity were marked depressed in AH while partly reversed in CH, and they were linearly related. Mitochondrial transcription activity in vitro was affected by ATP concentration diphasely.

CONCLUSION

Acute hypoxia may impair brain mitochondria energy metabolism by way of depressing mitochondrial transcription and then partially recover during chronic hypoxia. And mitochondrial transcription in vitro might be precisely regulated by ATP concentration.

Drosophila immunity: genes on the third chromosome required for the response to bacterial infection

We have screened the third chromosome of Drosophila melanogaster for mutations that prevent the normal immune response. We identified mutant lines on the basis of their failure to induce transcription of an antibacterial peptide gene in response to infection or their failure to form melanized clots at the site of wounding. These mutations define 14 genes [immune response deficient (ird) genes] that have distinct roles in the immune response. We have identified the molecular basis of several ird phenotypes. Two genes, scribble and kurtz/modulo, affect the cellular organization of the fat body, the tissue responsible for antimicrobial peptide production. Two ird genes encode components of the signaling pathways that mediate responses to bacterial infection, a Drosophila gene encoding a homolog of I kappa B kinase (DmIkk beta) and Relish, a Rel-family transcription factor. These genetic studies should provide a basis for a comprehensive understanding of the genetic control of immune responses in Drosophila.

The antibacterial arm of the drosophila innate immune response requires an IkappaB kinase

The ird5 gene was identified in a genetic screen for Drosophila immune response mutants. Mutations in ird5 prevent induction of six antibacterial peptide genes in response to infection but do not affect the induction of an antifungal peptide gene. Consistent with this finding, Escherichia coli survive 100 times better in ird5 adults than in wild-type animals. The ird5 gene encodes a Drosophila homolog of mammalian IkappaB kinases (IKKs). The ird5 phenotype and sequence suggest that the gene is specifically required for the activation of Relish, a Drosophila NF-kappaB family member.

Bridged silver(I) complexes of the polycyclic aromatic compounds tetraphenylethylene and 1,1,4,4-tetraphenyl-1,3-butadiene

For the purpose of investigating the coordination behavior of the sterically congested alkenes and exploring the possibility of cofacial complexation in the polycyclic aromatic system for formation of extended polymeric networks, tetraphenylethylene (tphe) and 1,1,4,4-tetraphenyl-1,3-butadiene (tphb) have been studied with regard to their complexation with a silver(I) ion. The crystal structures of [Ag(tphe)(ClO4)(p-xylene)], [Ag2(tphe)(ClO4)2], [Ag4(tphe)(CF3SO3)4], [Ag2(tphb)(ClO4)2], and [Ag2(tphb)(CF3SO3)2], together with the metal-free ligands tphe and tphb, have been determined by single-crystal X-ray diffraction. The pi-electron-rich cleft in organic components is found to offer a potential site for complexation, which can be utilized to generate an interesting array of organometallic compounds with one- and two-dimensional frameworks.

Mitotic histone H3 phosphorylation by the NIMA kinase in Aspergillus nidulans

Phosphorylation of histone H3 serine 10 correlates with chromosome condensation and is required for normal chromosome segregation in Tetrahymena. This phosphorylation is dependent upon activation of the NIMA kinase in Aspergillus nidulans. NIMA expression also induces Ser-10 phosphorylation inappropriately in S phase-arrested cells and in the absence of NIMX(cdc2) activity. At mitosis, NIMA becomes enriched on chromatin and subsequently localizes to the mitotic spindle and spindle pole bodies. The chromatin-like localization of NIMA early in mitosis is tightly correlated with histone H3 phosphorylation. Finally, NIMA can phosphorylate histone H3 Ser-10 in vitro, suggesting that NIMA is a mitotic histone H3 kinase, perhaps helping to explain how NIMA promotes chromatin condensation in A. nidulans and when expressed in other eukaryotes.

Structural studies of silver(I) coordination polymers with aryl iodide derived ligands

This paper reports novel silver polymers, built with iodine--silver interactions, with interesting structural motifs. Four silver(I) coordination polymers of the aryl iodide derived ligands, triiodobenzoic acid (HL1), tris(4-iodophenyl)amine (L2), and 5,7-diiodo-8-hydroxyquinoline (HL3), have been synthesized and characterized by X-ray crystallography. Treatment of Ag(CH3COO) with HL1 yielded [Ag(L1)] (1), whose structural analysis revealed 2D layers of ladders connected through weak Ag...I interaction. Reactions of AgClO4 and L2 in benzene and nitrobenzene afforded, respectively, two different products, [Ag(L2)(H2O)]ClO4.C6H6(2) and [Ag(L2)(ClO4)](3). While the structure of 2 could be described as a 2D layer of square and octagons perpendicular to [100], complex 3 is formed by 2D layers of the same topology of 2 (8(2).4), alternating as ABAB. In contrast, complex 4, [Ag2(H2L3)(CF3SO3)3], obtained by reaction of Ag(CF3SO3) and HL3, was found to consist of a 2D layer based on columnar arrays AgH2L3-Ag(triflate). The solid-state FT-IR and 109Ag NMR spectra of theses complexes are discussed on the basis of their crystal structures.

[The change of soft tissue profile before and after treatment with Begg technique]

OBJECTIVE:This study was to determine the facial soft tissue profile changes Begg technique after treatment. METHODS: 32 patients presented with Angle Class II divide I malocclusion. Lateral cephalograms were taken before treatment and after each treatment stage.Each experimental subject served as its own control by means of cephalometric analysis. RESULTS: Significant soft tissue profile improvement could be expected from first stage to second stage.But third stage of orthodontic treatment had little effective for the profile changes.The soft tissue profile changes which occured during treatment were (1) a retraction of lips and a reduction in the prominence of the lips.(2) an increase of nose prominence. (3) vertical opening at the chin. CONCLUSION: Begg technique was more close to clinical requirement in improvement of soft tissue profile.Achieved a harmony of soft tissue profile must be emphasized as an orthodontic treatment goal during second stage,then establishment of a proper occlusion would be finished.

Regulated nuclear import of Rel proteins in the Drosophila immune response

The Drosophila immune response uses many of the same components as the mammalian innate immune response, including signalling pathways that activate transcription factors of the Rel/NK-kappaB family. In response to infection, two Rel proteins, Dif and Dorsal, translocate from the cytoplasm to the nuclei of larval fat-body cells. The Toll signalling pathway, which controls dorsal-ventral patterning during Drosophila embryogenesis, regulates the nuclear import of Dorsal in the immune response, but here we show that the Toll pathway is not required for nuclear import of Dif. Cytoplasmic retention of both Dorsal and Dif depends on Cactus protein; nuclear import of Dorsal and Dif is accompanied by degradation of Cactus. Therefore the two signalling pathways that target Cactus for degradation must discriminate between Cactus-Dorsal and Cactus-Dif complexes. We identified new genes that are required for normal induction of transcription of an antibacterial peptide during the immune response. Mutations in three of these genes prevent nuclear import of Dif in response to infection, and define new components of signalling pathways involving Rel. Mutations in three other genes cause constitutive nuclear localization of Dif; these mutations may block Rel protein activity by a novel mechanism.

[Effects of exposure to TNT on sex hormones in male workers]

Field investigation on labour hygiene in two plants producing trinitrotoluene (TNT) in Henan Province showed most air TNT levels in the workplace exceeded national maximum allowable concentration (MAC 1 mg/m3) and the skin of the workers exposed to TNT was severely contaminated. Determinations of serum levels of sex hormones showed those of testosterone were lower, but those of interstitial cell-stimulating hormone (ICSH or LH) and follicle stimulating hormone (FSH) were higher in workers exposed to TNT than that in controls with statistical significance (P < 0.01).

C-terminal deletion mutants of the FokI restriction endonuclease

We have constructed two C-terminal deletion mutants of the FokI restriction endonuclease by using the polymerase-chain-reaction technique and expressed them in Escherichia coli. The two mutant proteins (MP) of 41 and 30 kDa, were purified to homogeneity and their DNA-binding properties were characterized. The 41-kDa MP specifically binds the DNA sequence, 5'-GGATG/3'-CCTAC, like the wild-type (wt) FokI, but does not cleave DNA. The 30-kDa MP does not bind DNA. The affinity of the 41-kDa MP for the DNA substrate is comparable to that of wt FokI. The 41-kDa MP interacts with its substrate like the wt FokI, as revealed by hydroxyl radical footprinting experiments. In the presence of a DNA substrate, the 41-kDa MP is cleaved by trypsin into a 30-kDa N-terminal fragment and an 11-kDa C-terminal fragment. Addition of the HPLC-purified 11-kDa C-terminal fragment to the 30-kDa MP restores its sequence-specific DNA-binding property. These results confirm that the N-terminal 41-kDa fragment of the FokI ENase constitutes the DNA recognition domain of the ENase.

Functional domains in Fok I restriction endonuclease

The PCR was used to alter transcriptional and translational signals surrounding the Flavobacterium okeanokoites restriction endonuclease (fokIR) gene, so as to achieve high expression in Escherichia coli. By changing the ribosome-binding site sequence preceding the fokIR gene to match the consensus E. coli signal and by placing a positive retroregulator stem-loop sequence downstream of the gene, Fok I yield was increased to 5-8% of total cellular protein. Fok I was purified to homogeneity with phosphocellulose, DEAE-Sephadex, and gel chromatography, yielding 50 mg of pure Fok I endonuclease per liter of culture medium. The recognition and cleavage domains of Fok I were analyzed by trypsin digestion. Fok I in the absence of a DNA substrate cleaves into a 58-kDa carboxyl-terminal and 8-kDa amino-terminal fragment. The 58-kDa fragment does not bind the DNA substrate. Fok I in the presence of a DNA substrate cleaves into a 41-kDa amino-terminal fragment and a 25-kDa carboxyl-terminal fragment. On further digestion, the 41-kDa fragment degrades into 30-kDa amino-terminal and 11-kDa carboxyl-terminal fragments. The cleaved fragments both bind DNA substrates, as does the 41-kDa fragment. Gel-mobility-shift assays indicate that all the protein contacts necessary for the sequence-specific recognition of DNA substrates are encoded within the 41-kDa fragment. Thus, the 41-kDa amino-terminal fragment constitutes the Fok I recognition domain. The 25-kDa fragment, purified by using a DEAE-Sephadex column, cleaves nonspecifically both methylated (pACYCfokIM) and nonmethylated (pTZ19R) DNA substrates in the presence of MgCl2. Thus, the 25-kDa carboxyl-terminal fragment constitutes the Fok I cleavage domain.

Overproduction and purification of the M.HhaII methyltransferase from Haemophilus haemolyticus

The HhaII methyltransferase gene from Haemophilus haemolyticus was subcloned in an expression vector under control of the hybrid trp-lac promoter. Induction with isopropyl-beta-D-thiogalactopyranoside results in overproduction of the methyltransferase to about 3% of total cellular protein. The methyltransferase was purified to near electrophoretic homogeneity by phosphocellulose, DEAE, and gel chromatography. Its monomer Mr by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is 25 kDa, in good agreement with that predicted from the nucleotide sequence. Crystals of the methyltransferase were obtained in the presence of a two-fold molar excess of the duplex oligodeoxynucleotide substrate 5'd-GGACTCC.CCTGAGG.