Role of vascular endothelial growth factor in diabetic nephropathy

BACKGROUND

Vascular endothelial growth factor (VEGF) is a potent cytokine that is considered to be an important mediator in the pathogenesis of endothelial dysfunction in diabetes.

METHODS

This study investigates the effect of high glucose on the signaling and production of VEGF in rat mesangial cells in culture and measures the urinary VEGF level in patients with different stages of diabetic nephropathy. To elucidate the role of VEGF in vivo further, expression of VEGF in control and diabetic kidneys was examined using immunohistochemistry.

RESULTS

A high ambient glucose concentration in the culture medium increased VEGF mRNA expression and protein production within 3 h in a concentration-dependent manner. A protein kinase C (PKC) inhibitor and PKC down-regulation inhibited glucose-induced increases in VEGF production. Urinary excretion of VEGF significantly increased according to the degree of proteinuria in patients with diabetes. A weak but significant correlation was found between urinary VEGF excretion and the levels of serum creatinine, creatinine clearance, microalbuminuria, and proteinuria. Immunohistochemistry revealed marked differences in the extent of mesangial VEGF staining between diabetic and control kidneys. Pronounced up-regulation of VEGF was observed in the glomerular epithelial cell in the early phase of diabetic kidney disease, whereas widespread expression of VEGF was found in the tubular segments, especially the proximal segment, in advanced diabetic nephropathy.

CONCLUSIONS

These results suggest that VEGF may play a role in the pathogenesis of diabetic nephropathy.

Missense mutation of the MET gene detected in human glioma

Multiple mechanisms, such as gene mutations, amplifications, and rearrangements, as well as perturbed mitogen and receptor function, are likely to contribute to glioma formation. The MET (also known as c-met proto-oncogene located at 7q31-34 has been shown to be amplified in human gliomas, and activating mutations within the tyrosine kinase domain of MET have been causally related to tumorigenesis in hereditary papillary renal cell carcinoma. To elucidate the role of MET gene in glioma formation, sporadic gliomas from 11 patients were examined for MET gene mutations and allelic duplications or deletions by polymerase chain reaction-single strand conformational polymorphism analysis and fluorescence in situ hybridization. Three of 11 sporadic gliomas showed a deletion of one copy of the MET gene, and a specific METgene missense mutation in the remaining gene copy was detected in one of those tumors. The corresponding sequence in non-tumor DNA was normal in all cases. Three of 11 sporadic gliomas showed duplication of one copy of the MET gene, but none of them contained mutations. One tumor showed METamplification without mutation. Three showed neither allelic change nor mutation. These data suggest that somatic MET gene mutation may play a role in the development of a subgroup of sporadic gliomas. However, MET mutations appear to be absent in the majority of sporadic gliomas.

Thermostable chitosanase from Bacillus sp. Strain CK4: cloning and expression of the gene and characterization of the enzyme

A thermostable chitosanase gene from the environmental isolate Bacillus sp. strain CK4, which was identified on the basis of phylogenetic analysis of the 16S rRNA gene sequence and phenotypic analysis, was cloned, and its complete DNA sequence was determined. The thermostable chitosanase gene was composed of an 822-bp open reading frame which encodes a protein of 242 amino acids and a signal peptide corresponding to a 30-kDa enzyme. The deduced amino acid sequence of the chitosanase from Bacillus sp. strain CK4 exhibits 76.6, 15.3, and 14.2% similarities to those from Bacillus subtilis, Bacillus ehemensis, and Bacillus circulans, respectively. C-terminal homology analysis shows that Bacillus sp. strain CK4 belongs to cluster III with B. subtilis. The gene was similar in size to that of the mesophile B. subtilis but showed a higher preference for codons ending in G or C. The enzyme contains 2 additional cysteine residues at positions 49 and 211. The recombinant chitosanase has been purified to homogeneity by using only two steps with column chromatography. The half-life of the enzyme was 90 min at 80 degrees C, which indicates its usefulness for industrial applications. The enzyme had a useful reactivity and a high specific activity for producing functional oligosaccharides as well, with trimers through hexamers as the major products.

8-O-Methylsclerotiorinamine, antagonist of the Grb2-SH2 domain, isolated from Penicillium multicolor

A new secondary metabolite, 8-O-methylsclerotiorinamine (1), was isolated from a strain of Penicillium multicolor, and its structure was established using NMR spectroscopy and chemical evidence. The metabolite inhibited significantly the binding between the Grb2-SH2 domain and the phosphopeptide derived from the Shc protein and also blocked the protein-protein interactions of Grb2-Shc in cell-based experiments, with IC(50) values of 5.3 and 50 microM, respectively.

Antitumor, genotoxicity and anticlastogenic activities of polysaccharide from Curcuma zedoaria

The antitumor effect of the partially purified polysaccharide from Curcuma zedoaria was studied in mice transplanted with sarcoma 180 cells. The polysaccharide fraction, CZ-1-III, at dose of 6.25 mg/kg/d showed 50% inhibition in solid tumor growth. When mice were injected with fractions, CZ-1 and CZ-1-III, at the dose of 100.0 mg/kg, 91.6% and 97.1% of tumor growth were inhibited, respectively, indicating that the cytotoxic effect of polysaccharide on sarcoma 180 cells increases upon increasing the amount of polysaccharide administered. To assess the genotoxicity of CZ-1-III fraction, several classical toxicological tests were performed. In Ames test, CZ-1-III did not show any transformation of revertant with or without S-9 metabolic activating system, indicating the lack of mutagenic effect of the compound. To assess clastogenic effect, micronucleus and chromosomal aberration assays were performed using Chinese hamster lung (CHL) fibroblast cells. However, up to 259.0 microg/ml concentration of CZ-1-III, neither micronucleus formation nor chromosomal aberration was induced regardless of the presence of S-9 metabolic activating system. Inhibition of CZ-1-III on micronucleus formation induced by mitomycin C was exhibited in a dose-dependent manner, maximally up to 52.0%. These results strongly suggest that CZ-1-III, the polysaccharide fraction from C. Zedoaria, decreases tumor size of mouse and prevents chromosomal mutation.

cis-fumagillin, a new methionine aminopeptidase (type 2) inhibitor produced by Penicillium sp. F2757

Selective inhibition against the yeast MetAP2 (methionine aminopeptidase type 2) was detected in the fermentation broth of a fungus F2757 that was later identified as Penicillium janczewskii. A new compound cis-fumagillin methyl ester (1) was isolated from the diazomethane treated fermentation extracts together with the known compound fumagillin methyl ester (2). The cis-fumagillin methyl ester, a stereoisomer of fumagillin methyl ester at the C2'-C3' position of the aliphatic side chain, selectively inhibited growth of the map1 mutant yeast strain (MetAP1 deletion strain) at a concentration as low as 1 ng. However, the wild type yeast w303 and the mutant map2 (MetAP2 deleted) strains were resistant up to 10 microg of the compound. In enzyme experiments, compound 1 inhibited the MetAP2 with an IC50 value of 6.3 nM, but it did not inhibit the MetAP1 (IC50 >200 microM). Compound 2 also inhibited the MetAP2 with an IC50 value of 9.2 nM and 105 microM against MetAP1.

Characterization of glk, a gene coding for glucose kinase of Corynebacterium glutamicum

The glk gene from Corynebacterium glutamicum was isolated by complementation using Escherichia coli ZSC113 (ptsG ptsM glk). We sequenced a total of 3072 bp containing the 969-bp open reading frame encoding glucose kinase (Glk). The glk gene has a deduced molecular mass of 34.2 kDa and contains a typical ATP binding site. Comparison with protein sequences revealed homologies to Glk from Streptomyces coelicolor (43%) and Bacillus megaterium (35%). The glk gene in C. glutamicum was inactivated on the chromosome via single crossover homologous recombination and the resulting glk mutant was characterized. Interestingly, the C. glutamicum glk mutant showed poor growth on rich medium such as LB medium or brain heart infusion medium in the presence or absence of glucose, fructose, maltose or sucrose as the sole carbon source. Growth yield was reduced significantly when maltose was used as the sole carbon source using minimal medium. The growth defect of glk mutant on rich medium was complemented by a plasmid-encoded glk gene. A chromosomal glk-lacZ fusion was constructed and used to monitor glk expression, and it was found that glk was expressed constitutively under all tested conditions with different carbon sources.

Natural and synthetic analogues of actinomycin D as Grb2-SH2 domain blockers

Natural analogues (D, C2, and VII) of actinomycin inhibit Grb2 SH2 domain binding with phosphopeptide-derived from Shc in vitro and in intracellular system. To study structure-activity relationships, 13 actinomycin analogues were synthesized and we found that the inhibition activity depended on the substituents of cyclic peptide groups in actinomycin and two analogues with Tyr residue are the most potent inhibitors with IC50 value of 0.5 and 0.8 microM, respectively.

Large cell neuroendocrine carcinoma of the lung: radiologic and pathologic findings

PURPOSE

The purpose of this work was to determine the radiologic and pathologic findings of large cell neuroendocrine carcinoma (LCNEC).

METHOD

We retrospectively evaluated chest radiographs, CT scans, and pathologic findings of five patients with pathologically confirmed LCNEC. They were confirmed by percutaneous needle biopsy (n = 2) and by surgery (n = 3). The average age of patients was 60 (51-70) years, and all five were smokers (mean 30 pack-years) and men. Radiologic findings were reviewed for the pattern of lesion, location, and associated findings by two radiologists under consensus. Pathologic findings were reviewed by two pathologists.

RESULTS

In all five patients, tumors were represented as a peripherally located nodule or mass without associated secondary pneumonitis or distal atelectasis radiographically. On CT scan, masses were oval or round and well demarcated with lobulated margin in all cases, their sizes ranged from 2 to 5 cm, and they did not show internal calcification and necrosis. On contrast-enhanced CT, three cases showed moderate enhancement more than the chest wall muscle. Lymphadenopathy was observed in ipsilateral hilar and mediastinal areas in three cases. Distant metastasis to liver was noted in one case. One case of LCNEC was Stage IV, two were Stage IIIa, and two were Stage Ia at the time of diagnosis.

CONCLUSION

Although the epidemiology of LCNEC is more similar to that of small cell carcinoma than atypical carcinoids, in its strong association with smoking, rapid progression, and poor prognosis, our five cases of LCNEC show peripherally located pulmonary nodule or mass with or without regional lymphadenopathy, which are findings similar to those of atypical carcinoids rather than small cell carcinoma.

A practical large-scale synthesis of 17alpha-acetoxy-11beta-(4-N, N-dimethylaminophenyl)-19-norpregna-4,9-diene-3,20-dione (CDB-2914)

A new practical synthesis of 17alpha-acetoxy-11beta-(4-N, N-dimethylaminophenyl)-19-norpregna-4,9-diene-3,20-dione (CDB-2914) is described. The synthesis gives easily isolable solids at all steps and is amenable to large-scale process.

Selective gene expression in hepatic tumor with trans-arterial delivery of DNA/liposome/transferrin complex

Since hepatocellular carcinoma (HCC) is frequently presented at an advanced stage, only a small portion of patients with HCC can be treated with local modalities. Gene therapy is, therefore, one of the more promising approaches for patients with advanced HCC. To develop a new strategy for targeting gene delivery to the hepatic tumor, the efficiency of the transarterial delivery of liposome-DNA complex was evaluated in VX2 carcinoma implanted into the liver of rabbits. A mixture of pSV-beta galactosidase plasmid (40 micrograms), lipofectin (80 microliters), and transferrin (852 micrograms), the optimal proportion of which determined in vitro, was infused via the hepatic artery of a rabbit with VX2 hepatic tumors. The efficiency of trans-arterial gene delivery was compared to that of intra-tumoral injection. Rabbits (5 in each group) were sacrificed 48 hours after gene delivery and hepatic tissues were examined using X-gal staining. beta-galactosidase staining was observed exclusively within the tumor following the trans-arterial gene transfer. In contrast, adjacent peritumoral cells in addition to hepatic tumor cells were transfected by the intra-tumoral injection of transgene. These data indicate that enhanced gene expression in hepatic tumors is possible using trans-arterial delivery of the liposome-DNA complex.

Huge biliary cystadenoma mimicking cholecystic lymphangioma in subhepatic space

Biliary cystadenoma is a rare cystic neoplasm and constitutes only 5% of all intrahepatic cysts of biliary origin. We report a case of a 44-year-old woman with huge biliary cystadenoma in the subhepatic space, mimicking a cholecystic lymphangioma. Findings of various imaging modalities including reconstructed CT image are presented and correlated with surgical and pathologic findings.

Inhibitory effect of Artemisia asiatica alkaloids on acetylcholinesterase activity from rat PC12 cells

We screened 42 Korean traditional tea plants to determine the inhibitory effect of acetylcholinesterase and attenuation of toxicity induced by amyloid-beta peptide, which were related to the treatment of Alzheimer's disease (AD). The methanolic extract from Artemisia asiatica among tested 42 tea plants, showed the highest inhibitory effect (48%) on acetylcholinesterase in vitro. The methanolic extract was further separated with n-hexane, chloroform, and ethyl acetate of water, in order. The chloroform solubles, which were high in inhibitory effect of acetylcholinesterase, were repeatedly subjected to open column chromatography on silica gel. From the highest inhibitory fraction (78%) on acetylcholinesterase, the single compound was obtained by the Sep-Pak Cartridge (C18: reverse phase column). This compound was found to react positively on Dragendorff's reagent (potassium bismuth iodide), which typically reacted with the alkaloid. This compound was purified by HPLC (mu-bondapack C18 reverse phase column: 3.9 x 150 mm). The IC50 (the concentration of 50% enzyme inhibition) value of this compound was 23 micrograms/ml and the inhibitory pattern on acetylcholinesterase was mixed with competitive/non-competitive type. We examined the effects of this compound on toxicity induced by A beta (25-35) in rat pheochromocytoma PC12 cells. Pretreatment of the PC12 cells for 2 h with an alkaloid of Artemisia asiatica (1200 microg/ml) reduced the toxicity induced by A beta. This study demonstrated that an alkaloid of Artemisia asiatica, which was metabolized to small molecule in digestive tract and then could pass through the blood-brain barrier, appeared to be an acetylcholinesterase inhibitor with a blocker of neurotoxicity induced by A beta in human brain causing Alzheimer's disease.

Potentials and limitations of adenovirus-p53 gene therapy for brain tumors

We investigated the antineoplastic potentials of recombinant adenovirus containing wild-type p53 cDNA (Ad5CMV-p53) for malignant gliomas. In four human glioma cell lines (U-251 and LG expressing endogenous mutant p53, and U-87 and EFC-2 expressing wild-type p53) and two rat glioma cell lines (9L and C6, each expressing mutant and wild-type p53), gene transfer efficiency determined by X-gal staining and Western blotting was varied (10-99% at 10-500 multiplicity of infection, MOI). Growth inhibitory effect was drastic (>90% at 100 MOI) in U-251 cells and only moderate or minimal in other cell lines harboring wild-type p53 or low gene transfer efficiency. Ex vivo transduction of U-251 cells with Ad5CMV-p53 suppressed the in vivo tumorigenicity of the cells. Histopathologic examination for Ad5CMV-p53 toxicity to rat brains showed inflammatory reactions in half of the tested brains at 10(8) MOI. U-251 cells were inoculated intracerebrally in nude mice and injected Ad5CMV-p53 into the tumor, in which neither the tumor suppression nor the survival benefit was observed. In conclusion, heterogeneity of the cellular subpopulations of malignant glioma in p53 status, variable and insufficient gene delivery to tumor, and adenoviral toxicity to brain at higher doses may be limiting factors to be solved in developing adenovirus-p53 gene therapy for malignant gliomas.

Aromatase inhibitors from Isodon excisus var. coreanus

The diethyl ether extract of Isodon excisus var. coreanus exhibited significant inhibitory activity in aromatase assay. Bioactivity-guided fractionation of the extract led to the isolation of three active compounds: inflexin (ent-1alpha-hydroxy-3beta,6a-diacetoxykaur-16-en-11,15-dione ) (1), ursolic acid (2), and ursolic acid 3-O-acetate (3).

Fas (APO-1/CD95) ligand and Fas expression in renal cell carcinomas: correlation with the prognostic factors

BACKGROUND AND OBJECTIVE

Fas ligand (FasL, CD95L) is a type II transmembrane protein of the tumor necrosis factor family that induces cells to send an apoptotic signal to cells expressing Fas (CD95, APO-1). It has been shown that cancers have a dysregulated expression of Fas and FasL system, conferring a survival advantage. It is important to understand FasL and Fas expression in tumors, because the growth of cancer might be controlled by Fas-mediated apoptosis.

METHODS

The expressions of FasL and Fas were studied by immunohistochemical analyses in 51 cases of renal cell carcinomas and the adjacent normal renal tissues, respectively. In addition, their expressions were compared with prognostic factors, such as tumor size, nuclear grade, TNM stage, and histologic types.

RESULTS

In nonneoplastic renal tissues, FasL was expressed in all nephron segments, whereas Fas also expressed in all tubules, except for glomeruli. In renal cell carcinomas, FasL protein was detected in 50 (98.0%) of 51 cases, whereas Fas expressed in 38 (74.5%) of 51 cases. In fact, the immunostaining of Fas was less intense than that in the adjacent normal segments of all cases. The staining pattern showing both high expression of FasL and low expression of Fas was found in 36 (70.6%) (P = .04) of 51 cases, most of which were Fuhrman grade 2 or 3 tumors. However, the expression pattern did not correlate statistically with the tumor size, histologic type, or clinical stage. On the other hand, most grade 4 tumors displayed high expression of both FasL and Fas (P<.001).

CONCLUSION

These data indicate that high expression of FasL and low expression of Fas protein in renal cell carcinomas may play a role in evading surveillance of the immune system. In addition, the FasL and Fas expressions appear to have a therapeutic implication for high-grade tumors rather than a prognostic one.

Adenovirus-mediated suicide-gene therapy using the herpes simplex virus thymidine kinase gene in cell and animal models of human prostate cancer: changes in tumour cell proliferative activity

OBJECTIVES

To determine the feasibility and efficacy of suicide-gene therapy using adenovirus (Ad)-mediated herpes simplex virus thymidine kinase (HSV-TK) and the prodrug acyclovir, and to evaluate changes in the biological phenotype for tumour cell proliferative activity after suicide-gene therapy in animal models of human prostate cancer.

MATERIALS AND METHODS

Using a replication-defective adenoviral vector (cytomegalovirus, CMV) containing the beta-galactosidase gene (Ad-CMV-beta-gal) as a control and Ad-CMV-TK as the therapeutic vector under the transcriptional control of the CMV promoter, transduction efficiency was assessed in vitro by infecting LNCaP and PC-3 androgen-dependent and independent human prostate cancer cells with Ad-CMV-beta-gal, and using X-gal staining. The TK activity in prostate cancer cells infected with Ad-CMV-TK was determined by measuring TK-mediated [3H]-gancyclovir phosphorylation. The sensitivity of LNCaP and PC-3 cells to Ad-CMV-TK in vitro was determined after infection with the therapeutic vector with or without acyclovir. The inhibition of PC-3 tumour growth in vivo induced by the Ad-CMV-TK/acyclovir suicide-gene system was assessed in separate and controlled experiments using human prostate cancer mouse models. Ki-67 proliferative antigen and proliferating cell nuclear antigen (PCNA), both useful proliferative indices, were evaluated using immunohistochemical staining (MIB-1 monoclonal antibody and monoclonal anti-PCNA antibody) in formalin-fixed, paraffin-embedded tissues from gene therapy-treated and control animals.

RESULTS

The mean TK activity was significantly higher in LNCaP and PC-3 cells infected with Ad-CMV-TK than in cells infected with Ad-CMV-beta-gal, used as a control (P < 0.05). The growth of human prostate cancer cells with Ad-CMV-TK was significantly inhibited by adding acyclovir in vitro (P < 0.05). In the in vivo experiments using the PC-3 human prostate cancer mouse model, tumour volume and growth was lower in mice treated with Ad-CMV-TK/acyclovir than in those treated with Ad-CMV-TK only, acyclovir only or untreated (controls) (P < 0.05). Histochemical staining of tumour tissues showed that Ad-CMV-TK/acyclovir destroyed PC-3 tumours through tumour cell death and apoptosis, with local lymphatic infiltration. The mean PCNA labelling index in prostate cancer cells of mice treated with Ad-CMV-TK/acyclovir was significantly lower than that in untreated controls (P < 0.05, Mann-Whitney U-test). The Ki-67 labelling index in prostate cancer cells of mice treated with Ad-CMV-TK/acyclovir was also lower than that in untreated controls (P < 0.05, Student's t-test). Adenovirus-mediated suicide-gene therapy using the HSV-TK gene decreased the proliferative activity of PC-3 human prostatic cancer cells in vivo.

CONCLUSIONS

Adenovirus-mediated suicide-gene therapy using an HSV-TK/acyclovir system provided effective therapy in an experimental human prostate cancer mouse model, by significantly inhibiting tumour growth and decreasing the proliferative activity of human prostate cancer cells. Such therapy could be developed as a novel method for treating patients with androgen-independent prostate cancer.

Comparison of 1- and 2-incision posterior cruciate ligament reconstructions

This study compared the results of the 1-incision technique and the conventional 2- incision technique for the arthroscopic treatment of the posterior cruciate ligament (PCL) injury. The 2-incision technique was performed in 10 patients (group I) and the 1-incision technique in 45 patients (group II). The average duration of follow-up was 45 months in group I and 36 months in group II. Bone-patellar tendon-bone (BTB) autografts were used for all patients in group I. In group II, 34 BTB autografts and 11 BTB allografts were used. Postoperative Lysholm mean values were 90.0 in group I and 90.6 in group II. HSS mean values were 87.7 in group I and 92.6 in group II (P = .037). The Tegner activity level scales were 6.4 in group I and 6.5 in group II. The average side-to-side difference of the corrected posterior translation measured by the KT-2000 arthrometer were 2.10 mm in group I and 2.38 mm in group II. There were no statistically significant differences between the 2 groups in postoperative mean values except HSS scores. The arthroscopic PCL reconstruction using the 1-incision technique showed good results comparable with the conventional 2-incision technique. This technique needs no another incision or dissection over the medial femoral condyle.

Alternating current aspects of antimicrobial molecular complexes

A novel method was designed involving the titration of alternating current titration in a cell where one electrode was shielded by a capillary enclosure restricting access to it by charge carriers. With this cell, charge transfer complex titration of several thiazines all with some antimicrobial properties was effected in acetonitrile, against the electron accepting molecule iodine. The maxima of the Job plots generated by these titrations exhibited displacement of their positions for the forward and reverse titrations with respect to electron donor-acceptor complexation conductivity and apparent stoichiometry. A plot of inverse conductivity maxima differences against literature-cited dipole moments squared yielded a straight line passing through the origin. The titration plot profiles are discussed in terms of the type, number, and mobility of charge carriers produced in the complexation interaction. This novel method may be used to determine dipole moments of bioactive homologues empirically. There was correlation between thiazine drug dipole moments and minimal inhibitory concentrations of these drugs for some bacterial and yeast species. Several new avenues of investigation of possible relevance to microbiology are suggested.

Charge transfer complexes of K vitamins with several classes of antimicrobials

The charge transfer donor (D)-acceptor (A) complexes formed between three classes of vitamin K (all electron acceptors in this study) with several thiazine psychotropes, used also as antimicrobials, antimalarials, antibiotics, and anticoagulants, were studied by means of alternating current titrations. The monochloride thiazines formed 2:1 (D:A) complexes, interacting from 26 to 47.5%; the dihydrochloride formed a 3:1 (D:A) complex. The antimalarials quinine and its isomer quinidine yielded 2:1 (D:A) complexes, interacting 51 and 60%, respectively. Quinacrine did not complex with vitamin K. The antibiotics sulfisoxasole and sulfamethisole gave 1:1 complexes, respectively interacting 6.2 and 11.7%. The anticoagulants warfarin, coumarin and dicumarol, rather than forming complexes proceeded rapidly to chemical reaction. When the above thiazine antimicrobials, antimalarials and antibiotics are present in patients receiving vitamin K post-operatively the dosage of administered vitamin K should be increased to counteract the donor-acceptor interaction effect.

Disruption of interkringle disulfide bond of plasminogen kringle 1-3 changes the lysine binding capability of kringle 2, but not its antiangiogenic activity

Kringle 1-3 of human plasminogen is a potent inhibitor of endothelial cell proliferation. To understand a possible role for the unique cystine bridge between kringle 2 and kringle 3, we disrupted the interkringle disulfide bond by mutating Cys(169) and Cys(297) to serine residues. The yield of the mutant during the refolding process was decreased significantly. Anti-endothelial cell proliferative activity of the mutant was similar to that of the wild type. There was no significant difference in in vivo antiangiogenic activity between the wild type and the mutant in chorioallantoic membrane assay. However, in the mutant, the weak lysine binding capability of kringle 2 was not detected and its mobility in nonreducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis is different from that of the wild type. These results support the notion that the overall antiangiogenic function of angiostatin is mediated by individual kringles, and suggest that the lysine binding capability of kringle 2 is likely not important for the antiangiogenic activity of kringle 1-3.

Crystal structure of NAD(+)-dependent DNA ligase: modular architecture and functional implications

DNA ligases catalyze the crucial step of joining the breaks in duplex DNA during DNA replication, repair and recombination, utilizing either ATP or NAD(+) as a cofactor. Despite the difference in cofactor specificity and limited overall sequence similarity, the two classes of DNA ligase share basically the same catalytic mechanism. In this study, the crystal structure of an NAD(+)-dependent DNA ligase from Thermus filiformis, a 667 residue multidomain protein, has been determined by the multiwavelength anomalous diffraction (MAD) method. It reveals highly modular architecture and a unique circular arrangement of its four distinct domains. It also provides clues for protein flexibility and DNA-binding sites. A model for the multidomain ligase action involving large conformational changes is proposed.