X-ray crystalline structures of pyrrolidone carboxyl peptidase from a hyperthermophile, Pyrococcus furiosus, and its cys-free mutant.

In order to elucidate the mechanism of the thermostability of proteins from hyperthermophiles, X-ray crystalline structures of pyrrolidone carboxyl peptidase from a hyperthermophile, Pyrococcus furiosus (PfPCP), and its mutant protein with Ser substituted at Cys142 and Cys188 were determined at 2.2 and 2.7 A resolution, respectively. The obtained structures were compared with those previously reported for pyrrolidone carboxyl peptidases from a hyperthermophilie, Thermococcus litoralis (TlPCP), and from a mesophile, Bacillus amyloliquefaciens (BaPCP). The PfPCP structure is a tetramer of four identical subunits similar to that of the TlPCP and BaPCP. The largest structural changes among the three PCPs were detected in the C-terminal protrusion, which interacts with that of another subunit. A comparison of the three structures indicated that the high stability of PfPCP is caused by increases in hydrophobic interactions and hydrogen bonds, the formation of an intersubunit ion-pair network, and improvement to an ideal conformation. On the basis of the structures of the three proteins, it can be concluded that PfPCP does not have any special factors responsible for its extremely high stability and that the conformational structure of PfPCP is superior in its combination of positive and negative stabilizing factors compared with BaPCP.

Nucleic acid binding by zinc finger-like motif of human papillomavirus type 16 E7 oncoprotein.

Human papillomavirus (HPV) types 16 and 6b E7 proteins and their chimeric or mutant proteins were analyzed for oligonucleotide-binding activity by surface plasmon resonance-based biomolecular interaction analysis. The results indicated that type 16 E7 protein has stronger nucleic acid-binding activity than that of type 6b E7 protein. In addition, the results also indicated that the zinc finger-like motif in the C-terminal region of the type 16 E7 protein plays an important role in this activity.

Functional oligomerization of purified human papillomavirus types 16 and 6b E7 proteins expressed in Escherichia coli.

Purified non-fused soluble human papillomavirus type 16 and 6b E7 proteins expressed in Escherichia coli were found to form oligomers. For both proteins, several degrees of oligomerization were demonstrated by gel filtration, dynamic laser light scattering and scanning electron microscopy. Oligomerization was dependent on the concentration of E7 protein. Oligomerized E7 proteins were able to bind the retinoblastoma gene product pRB and stimulated DNA synthesis when introduced into cells.

Transformation assays of the cell mitotic and proliferation activities of purified oncogene products.

Using two direct introduction methods, DNA synthesis or cell proliferation activities of three purified proteins from E. coli, namely, human papillomavirus (HPV) E7 proteins of type 16, a mutant type 16 (24 C-G) (transformation defective) and type 6b, were measured in mouse fibroblast, C127 cells. By a microinjection method, the order of the cell mitotic indexes for the three E7 proteins as determined by 5-bromo-2'-deoxy-uridine (BrdU) staining was type 16, 6b and 16 (24 C-G). By the osmotic shock method, the 3H-TdR incorporation and coloration by (3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetolazorium (MTS) for the three proteins correlated with the pRb binding and focus forming activities previously reported (Munger et al. 1991). These results indicate that the simple osmotic shock method for direct protein introduction may be generally useful for transformation assays of oncoproteins.

Therapeutic effects of bovine enterovirus infections on autochthonous rat ovarian carcinomas induced by 7,12-dimethylbenz (a) anthracene (DMBA).

It has been previously reported that infection by a bovine enterovirus (MZ-468), which does not infect normal human cells, was remarkably effective for the therapy of adult T cell leukemia (ATL) in experimental rabbit models (Shingu et al. 1991). Therapeutic treatment studies were performed twice on 30 and 20 autochthonous rat ovarian carcinomas induced by DMBA. The average tumor size of the virus treatment group was significantly smaller than the control group when analyzed by a nonparametric Mann-Whitney method (p < 0.06 and 0.002 for the 1st and 2nd experiments, respectively). These results indicate that an enterovirus infection may be clinically useful for the therapy of human ovarian cancers with bad prognoses.

Association of RNA with human papillomavirus E7 protein of type 16 but not type 6b.

Nonfused human papillomavirus (HPV) type 16 and 6b E7 proteins were expressed in E. coli and fractionated by ion exchange and gel filtration chromatography. The E7 protein of type 6b was purified, but that of type 16 was found to be associated with RNA molecules which could not be excluded by repeated chromatography. The type 16 E7 protein in CaSki cells was also associated with RNA molecules of the same size.

Pattern recognition of continuity of discrete data points by scale changed plots.

Graphs composed of a large number of data points plotted on an appropriate scale enables us to pattern recognize a specific continuous curve. This principle was used to follow signals from proton nuclear magnetic resonance as a function of pH in a large biomolecule, staphylococcal nuclease. The analysis was automated by auto peak-picking routines and by transferring the results to a graphic program, Graphic Operating System (Roome & Peterson, 1985). Expansion and contraction of the scale made it possible to differentiate specific tyrosine and histidine titration curves. This type of analysis is applicable for assignment of specific curves from a large number of data points which change as a function of perturbations.

Significance of anti-eye muscle antibody in patients with thyroid-associated ophthalmopathy by quantitative western blot.

To investigate the prevalence of antibody against rat eye muscle membrane antigen, as determined from SDS-polyacrylamide gel electrophoresis and western blotting, in sera from patients with thyroid-associated ophthalmopathy (TAO), we quantitatively analyzed the binding activity with a rat eye muscle membrane 64 kDa protein using chromato-scanner. Eye muscle antibody activity was expressed as ratio of density of the 64 kDa band to that at 66 kDa found with all normal sera and phosphate buffered saline. The mean (+/- SD) eye muscle antibody activity was 2.7 +/- 2.7 in TAO (P < 0.01 v.s. normal), 1.5 +/- 1.7 in Graves' disease without evident eye disease, 1.6 +/- 2.5 in Hashimoto's thyroiditis and 0.45 +/- 0.26 in normal subjects. A positive band at 64 kDa was found in 71% of patients with TAO, 36% of those of Graves' disease without evident eye disease and in 35% of patients with Hashimoto's thyroiditis without eye disease. The prevalence of this antibody activity tended to correlate to the severity of ophthalmopathy. Furthermore, the level of eye muscle antibody activity decreased in parallel with the improvement of eye signs in two patients. Sera reactive with rat eye muscle membrane 64 kDa protein reacted also with a human eye muscle membrane 64 kDa protein but not with human thyroid, liver, spleen or pancreas membrane preparations. In conclusion, antibody to rat eye muscle membrane 64 kDa protein is present in TAO and may be a useful clinical marker of ophthalmopathy.

Construction of an expression vector for human papillomavirus type 16 E7-glutathione S transferase fusion protein.

An expression vector for human papillomavirus type 16 (HPV 16) E7-glutathione S transferase fusion protein was constructed. The E7 gene was confirmed by southern blot analysis with a digoxygenin 11-dUTP labeled and simultaneously amplified E7 DNA probe by polymerase chain reaction (PCR). The fusion protein was expressed in E. coli, recovered as inclusion bodies, and was confirmed by western blot analysis using a monoclonal antibody against HPV 16-E7 protein. A polyclonal antibody against the HPV 16-E7 protein was raised in the serum of mice hyper-immuned with the fusion protein. This antibody will be available for screening of patients with cervical cancer.

Therapeutic effects of bovine enterovirus infection on rabbits with experimentally induced adult T cell leukaemia.

A bovine enterovirus, MZ-468, showed cytopathic effects on cell line F-647a, which was established by coculture of human T cell lymphotropic virus type 1-transformed MT-2 cells and X-irradiated rabbit lymphocytes. Microcalorimetric assay showed that residual, viable, MZ-468-infected F-647a cells produced less heat than non-infected cells. The therapeutic effects of MZ-468 infection were examined in rabbits in which adult T cell-like leukaemia (ATL) had been induced by inoculation of F-647a cells (1 x 10(8) cells). Six newborn rabbits were separated into three groups: group A was inoculated with F-647a cells only; group B was treated with MZ-468 at the time of inoculation with cells; group C was treated with the same amount of virus 24 h after the inoculation with cells and then once every 4 days. Both of the animals in group A and one in group C died 10 and 11 days, and 22 days, respectively, after the inoculation with cells. Both rabbits in group B and one in group C survived for more than 4 months. The rabbits that died were examined pathologically; leukaemic infiltrations were found in the lungs of the group B rabbits, and in the lungs, spleens and livers of both group A rabbits. Two identical experiments produced almost the same findings. These results suggest that bovine enterovirus might be used clinically to prolong the life-span of ATL patients.

Refolding and purification of human papillomavirus type 16 E7-lacZ fusion protein expressed in Escherichia coli.

Human papillomavirus (HPV) type 16 E7-lacZ fusion protein was produced in Escherichia coli, extracted as inclusion bodies, refolded with reducing reagents, and subjected to gel filtration. The refolded protein was purified by ion-exchange column chromatography, resulting in a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. 1H nuclear magnetic resonance spectral changes were observed in the high field methyl region in the presence of Zn2+ ion, suggesting that the refolded form of the fusion protein is possibly renaturated into the putative zinc finger motif (C. Edmond and K. H. Vousden, 1989, J. Virol. 63, 2650-2656) and supporting the data of J. A. Rawls, R. Pusztai, and M. Green (1990, J. Virol. 64, 6121-6129) on zinc binding to E7 protein using radioisotopically labeled zinc ion.

Densitometric determination of human papillomavirus DNA quantities by chromato-scanning in the fluorescence mode.

The quantitation of human papillomavirus DNA isolated from warts by chromato-scanning (fluorescence mode) photographs of ethidium bromide-stained agarose gels is described. Excitation at 200 nm (with a cutoff filter at 400 nm) generates fluorescence from the white portion of the printing paper. The fluorescent intensity correlated with the quantities of DNA in the band of interest. The amounts of DNA were determined using calibration curves of approximately the same size as lambda phage DNA fragments. This general method of quantification is applicable to photographs of other types of polynucleotides capable of being separated and stained in a gel medium.

Correlation between DNA quantities in agarose gel and chromatographic areas of photographed DNA bands.

To quantitate DNA from photographs, correlations between chromato-scanned (in the fluorescence mode) and virtual areas from white DNA bands on photographs were examined. A linear correlation between the two measurements with coefficients higher than 0.89 was observed. The dynamic range of the fluorescence detection yielded good linearity for a wide range of amounts of DNA (microgram-ng) on the photograph.

A pH-dependent conformational change of staphylococcal nuclease: hydrogen-1 two-dimensional nuclear Overhauser spectroscopy studies.

Two-dimensional nuclear magnetic resonance (2d-NMR) dipolar correlation spectroscopy (NOESY) for the calcium binding protein, staphylococcal nuclease, was used to study the conformations in solution as a function of pH. A series of 2d-NOESY spectra of the nuclease H124L-Ca(++)-thymidine 3'5'-bisphosphate ternary complex demonstrated significant pH dependent changes: NOE cross peaks between 46His delta H and an aliphatic proton at 2.66 ppm appeared at pH 10.2, but not at pH 5.5. Some other NOE cross peaks between aromatic and aliphatic protons displayed chemical shift changes in omega 2 or both dimensions (omega 1, omega 2). These results indicated that a local rearrangement accompanies the ionization of the functional groups and has a role in enzyme function.

An in vitro kinetic assay of ATPase by phosphorus-31 NMR.

The ATPase activity of RecA protein was examined by monitoring the changes of NMR phosphorus signals of ATP, ADP and inorganic phosphate. The areas of phosphorus-31 NMR peaks from inorganic phosphate and ADP, which increased with time, and the signals from ATP, which decreased with time, were fitted by a linear least square method to obtain the initial rate constants. The rate constants were examined for dependence on RecA protein concentration, temperature and pH. This assay system is useful for testing extrinsic physico-chemical effects on ATPase activity; because only essential components are present in a confined system, and the rate constants can be measured with a single step.

Effects of protein phosphorylation with p43v-abl and protein kinase A catalytic subunit on fluorescence intensity.

To study the effect of phosphorylation on protein conformation, a fluorescence spectroscopic study was performed on phosphorylated enolase and histoneH1 proteins. The peak of fluorescence was 330 and 360 nm for each protein, respectively, when excited at 287 nm. The intensities of the fluorescence were measured during the phosphorylation reactions with the protein kinase A and p43v-abl, for serine, threonine and tyrosine, respectively. Slightly increased intensities at 330 and 360 nm for enolase and histoneH1 protein were observed by phosphorylation with p43v-abl, whereas decreased intensities occurred with the protein kinase A catalytic subunit. These data suggest that micro-structural changes are induced at the residue, either tyrosine, serine or threonine in the protein.

Human papillomavirus DNA from warts for typing by endonuclease restriction patterns: purification by alkaline plasmid methods.

The alkaline plasmid DNA extraction method of Birnboim and Doly was applied for the isolation of human papillomavirus (HPV) from warts. Tissue from common and plantar warts was digested with proteinase K, and the extrachromosomal circular covalently-closed form of HPV-DNA was rapidly extracted by alkaline sodium dodecyl sulphate and phenol-chloroform treatment. Recovery of HPV-DNA from the tissue was sufficient for determination of endonuclease restriction patterns by agarose gel electrophoresis.

Subcloning and trial of expression of the protein kinase catalytic domain of RSV-src gene.

The gene of catalytic domain of the protein kinase of RSV-scr was cloned into the BamHI cloning site of translation vector pET-8c which containing T7 RNA polymerase promotor, and transformed BL21 (DE3) pLys S (Studier and Moffatt, 1986). The putative molecular weight of the protein was about 33 kd as evaluated on the basis of its nucleotide size showed the identical mobility in SDS-polyacrylamide gel electrophoresis. However, yield of protein production was not high, probably, because of its instability in Escherichia coli.