[Advances in molecular mechanism and treatment of chronic mucus hypersecretion].

Chronic obstructive pulmonary disease (COPD) is one of the chronic diseases with high morbidity and mortality in China, which imposes heavy economic burden on society. Research has shown that chronic mucus hypersecretion (CMH) is an independent risk factor for persistent clinical symptoms, poor quality of life, rapid decline in lung function, acute exacerbation and increased hospitalization rate in COPD patients. CMH is a clinical phenotype of COPD with specific pathological and physiological changes. At present, the formation mechanism of CMH is not clear. There is a lack of specific and effective targeted treatments. This article aimed to review the latest research findings on CMH at home and abroad from the overview, impact on COPD patients, molecular mechanisms of formation, current treatment status and progress, and discuss potential targets for CMH treatment, to provide new ideas and directions for improving CMH and treating COPD.

[A case of left pulmonary artery sling combined with congenital tracheal stenosis in an adult].

Pulmonary artery sling in adults is a rare congenital vascular malformation usually accompanied by tracheal and bronchial stenosis. Due to its high mortality risk and relatively poor prognosis, it has rarely been reported in adults. We reported a middle-aged patient who presented with shortness of breath, predominantly after activity, since childhood. He was diagnosed with "tracheal stenosis" in another hospital and received symptomatic treatment. The diagnosis of left pulmonary artery sling with congenital tracheal stenosis was confirmed by multi-slice spiral CT (MSCT), airway examination with flexible bronchoscope and 3D image post-processing system. Data from this case and the related literatures have been summarized and analyzed. This will help clinicians to improve their level of diagnosis and treatment.

[Efficacy of selective bronchial occlusion in the treatment of biliary bronchial fistula].

Objective: To analyze the effect of selective bronchial occlusion (SBO) in the treatment of biliary bronchial fistula (BBF). Methods: Eight patients with BBF that without biliary obstruction admitted to the Department of Respiratory and Critical Care Medicine, the First Affiliated Hospital of Naval Medical University from January 1, 2015 to December 31, 2021 were included in this study. Bronchial silicone plug (6 cases) and autologous blood+thrombin (2 cases) were used as sealing materials for SBO treatment for the first time. Among the 7 patients who underwent subsequent closure treatment, 5 cases were blocked by bronchial silicone plug, 1 case was blocked by "bronchial silicone plug+bullet-covered stent" and 1 case was blocked by "bronchial silicone plug+bronchial one-way valve". The clinical data related to SBO treatment were collected and patients were followed up, and the therapeutic effect of SBO on BBF was analyzed. Results: The age of BBF onset was (58±9) years old, including 6 males. Among the 6 patients who used bronchial silicone plug as plugging material in the first SBO treatment, 1 case was successfully plugged, 2 cases did not achieve symptoms relief after plugging, 2 cases coughed up the plugging device immediately after surgery, and 1 case developed a new fistula. Autologous blood and thrombin were used as sealing materials in 2 patients, and both failed. Among the 7 patients who received subsequent closure treatment, bronchial silicone plug+bullet-covered stent (1 case) and bronchial silicone plug+bronchial unidirectional valve (1 case) were successful. After 2-6 times of bronchial silicone plug (5 cases), fistula were successfully blocked in 3 cases, and the frequency and volume of bile-like sputum decreased by 50% or more in 2 cases. The main postoperative complications were fever and cough (expectoration) in 7 and 6 cases, respectively. During the follow-up period, 2 patients were lost to follow-up, and the remaining 6 patients were followed up for 2-31 months. During the follow-up period, the effect of closure treatment was basically stable, and there was no death case. Conclusion: SBO therapy provides a safe and feasible palliative treatment for BBF.

[The 472nd case: dyspnea, pulmonary shadows, abnormalities of whole blood cells].

A 54-year-old man was admitted to respiratory department with chief complaints of recurrent cough and dyspnea. Chest imaging showed multiple patchy shadows and interstitial changes. Evidence of infectious diseases was not definite, and antibiotic treatments were not effective. In the meantime, myelodysplasia syndrome was diagnosed with pancytopenia. The pathologic findings of transbronchoscopic lung biopsyshowed chronic inflammatory interstitial changes, suggesting a clinical diagnosis of organizing pneumonia. After glucocorticoids treatment, his condition aggravated. The second percutaneous lung biopsy showed the infiltration of a large number of neutrophils. Therefore, the final diagnosis of myelodysplasia syndrome with Sweet syndrome was made. Then glucocorticoids and supportive treatment were given This case may improve physicians' understanding of myelodysplasia syndrome complicated with Sweet syndrome.

[Clinical analysis of therapeutic bronchoscopy for tracheal neoplasm].

Objective: To analyze the clinical features in adults with tracheal neoplasm and to evaluate the efficacy of interventional bronchoscopic treatment. Methods: We retrospectively analyzed the clinical features of 43 adults undergoing therapeutic bronchoscopy for tracheal neoplasm diagnosed in Changhai Hospital affiliated to the Second Military Medical University from January 2004 to July 2014.The degree of stenosis, the grade of dyspnea, and Karnofsky performance status scale were evaluated before and after the last procedure. All cases were followed up for 2 years. Results: The 43 cases took (4.6±3.9) months on average to be diagnosed since initial symptom. The initial misdiagnosis rate was 41.9%(18/43), and 11 cases were mistaken for asthma (11/43). Malignant tumors were more common than benign tumors for tracheal neoplasm in adults. Squamous cell carcinoma and adenoid cystic carcinoma were the top 2 histological types. Central airway obstruction was completely or partially alleviated with significant relief of dyspnea after the procedures, and all 6 cases of tracheal benign tumors got complete alleviation (the overall response rate was 100%). The grade of dyspnea was 3.2±0.7 before and 1.5±0.8 after the procedures(t=6.63, P<0.05). The value of KPS was 63±12 before and 83±11 after the procedures(t=5.78, P<0.05). The 2-year survival rate of 6 cases of tracheal benign tumors was 100.0%, and 1 case of papillomatosis had a relapse. The 1-year survival rate and 2-year survival rate of 37 cases of tracheal malignant tumors were 59.5% and 43.2% respectively with a median survival of 13.6 months. Conclusion: Therapeutic bronchoscopic interventions provide significantly alleviation of central airway obstruction and result in improvement in shortness of breath and quality of life for tracheal neoplasm.

Neuroprotection effect of interleukin (IL)-17 secreted by reactive astrocytes is emerged from a high-level IL-17-containing environment during acute neuroinflammation.

An increase in interleukin (IL)-17A-producing cells, particularly at sites of tissue inflammation, is observed frequently, yet the mechanism is not fully understood. This study aims to dissect the role of IL-17 in autoimmunity-mediated neuroinflammation. The cytokine milieu containing elevated IL-17, which often appears in active states of autoimmunity, was mimicked in vitro by a supernatant obtained from rat peripheral blood monocytes stimulated with phorbol mystistate acetate (PMA)/ionomycin. The application of such inflammatory media on only primary cultured cerebellar granule neurones resulted in significant apoptosis, but the presence of astrocytes largely prevented the effect. The supernatants of the stimulated astrocytes, especially those that contained the highest level of IL-17, achieved the best protection, and this effect could be blocked by anti-IL-17 antibodies. Protein IL-17 inhibited intracellular calcium increase and protected the neurones under inflammatory attack from apoptosis. IL-17, but not interferon (IFN)-γ, in the inflammatory media contributed to astrocyte secretion of IL-17, which depended on the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway activation. The astrocytes that were treated with IL-17 alone or with prolonged treatment of the inflammatory media failed to produce sufficient levels of IL-17. Moreover, confirmatory data were obtained in vivo in a monophasic experimental autoimmune uveitis (EAU) in Lewis rats; in this preparation, the high-level IL-17-containing the cytokine milieu was demonstrated, along with IL-17 secretion by the resident neural cells. The antagonism of IL-17 at a late stage disturbed the disease resolution and resulted in significant neural apoptosis. Our data show a dynamic role of IL-17 in the maintenance of homeostasis and neuroprotection in active neuroinflammation.

[Clinical study of the efficacies of ruxolitinib plus low-dose PTCY for acute GVHD prevention after haploidentical transplantation in malignant hematological diseases].

Objective: To investigate and verify a novel acute graft versus host disease (aGVHD) prevention protocol in the context of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) . Methods: Patients who underwent haplo-HSCT in our center between January 2022 and December 2022 were included. All patients received reduced doses of cyclophosphamide, Rabbit anti-human tymoglobulin, ruxolitinib, methotrexate, cyclosporine, and MMF to prevent aGVHD. The transplantation outcomes, complications, and survival rate of all patients were investigated. Results: A total of 52 patients with haplo-HSCT were enrolled, 29 (55.8%) male and 23 (44.2%) female, with a median age of 28 (5-59) years. There were 25 cases of acute myeloid leukemia, 17 cases of acute lymphocyte leukemia, 6 cases of myelodysplastic syndrome, 2 cases of chronic myeloid leukemia and 2 cases of myeloproliferative neoplasms. 98.1% of patients had successful engraftment. The incidence of Ⅱ-Ⅳ aGVHD and Ⅲ-Ⅳ aGVHD was 19.2% (95% CI 8.2% -30.3% ) and 7.7% (95% CI 0.2% -15.2% ), respectively. No patients experienced severe gastrointestinal mucositis. The Epstein-Barr virus and CMV reactivation rates were 40.4% and 21.3%, respectively. 9.6% of patients relapsed during followup, with 1-year overall survival, progression-free survival, and non-relapse mortality rates of 86.5% (95% CI 76.9% -96.1% ), 78.8% (95% CI 67.4% -90.3% ) and 11.5% (95% CI 2.6% -20.5% ), respectively. Conclusion: Ruxolitinib combined with a low dose of PTCY is a safe and effective first-line aGVHD prevention strategy.

[Effects and mechanism of negative pressure microenvironment on the neogenesis of human umbilical vein endothelial cells].

Objective: To investigate the effects and mechanism of negative pressure microenvironment on the neogenesis of human umbilical vein endothelial cells (HUVECs). Methods: The experimental research methods were adopted. The third to the fifth passage of HUVECs in the logarithmic growth stage were used for the subsequent experiments. Three batches of cells were taken, with each batch of cells being divided into normal control group and negative pressure treatment alone group (both routinely cultured for 24 h), and 17-allylamino-17-demethoxy-geldanamycin (17-AAG) alone group and 17-AAG+negative pressure treatment group (both cultured with 17-AAG for 24 h). In addition, the intermittent negative pressure suction, with the negative pressure value of -5.33 kPa (suction for 30 s, pause for 10 s) was continuously applied for 8 h on cells in the two negative pressure treatment groups using an automatic three-dimensional cell gradient negative pressure loading device designed and developed by ourselves. After the treatment of the first batch of cells, the cell proliferation level was detected by cell counting kit 8 method at 0 (immediately), 24, 48, and 72 h of culture, with the number of samples being 6. After the treatment of the second batch of cells, the scratch experiment was performed. At 12 h after scratching, the cell migration was observed under an inverted phase contrast microscope and the cell migration rate was calculated, with the number of samples being 3. After the treatment of the third batch of cells, the tubule formation experiment was conducted. After 6 h of culture, the tubulogenesis was observed under an inverted phase contrast microscope and the total tubule length and the number of branch nodes of cells were calculated, with the number of samples being 3. The cells were taken and divided into normal control group, negative pressure treatment alone group, and 17-AAG+negative pressure treatment group. The cells were treated the same as in the previous corresponding group. After the treatment, Western blotting was used to detect the protein expressions of heat shock protein 90 (HSP90), caveolin 1, endothelial nitric oxide synthase (eNOS), and eNOS phosphorylation site 1177 in the cells, and the eNOS phosphorylation site 1177/eNOS ratio was calculated, with the number of samples being 3; co-immunoprecipitation (co-precipitating HSP90 and caveolin 1, caveolin 1 and eNOS) and Western blotting were used to detect the protein expressions of caveolin 1 and eNOS in the cells, with the number of samples being 3; the protein co-localization of HSP90 and caveolin 1 and that of caveolin 1 and eNOS in the cells was assessed by immunofluorescence double staining. The molecular docking prediction of caveolin 1 and eNOS was processed by HADDOCK 2.4 protein-protein docking program. Data were statistically analyzed with analysis of variance for factorial design, one-way analysis of variance, and least significant difference method. Results: Compared with that in normal control group, the cell proliferation level in 17-AAG alone group was significantly decreased at culture hour of 24, 48, and 72 after the treatment (P<0.01), while the cell proliferation level in negative pressure treatment alone group was significantly increased at culture hour of 24, 48, and 72 after the treatment (P<0.01). Compared with that in 17-AAG alone group, the cell proliferation level in 17-AAG+negative pressure treatment group was significantly increased at culture hour of 48 and 72 after the treatment (P<0.05 or P<0.01). Compared with that in negative pressure treatment alone group, the cell proliferation level in 17-AAG+negative pressure treatment group was significantly decreased at culture hour of 24, 48, and 72 after the treatment (P<0.01). At 12 h after scratching, compared with (39.9±2.7)% in normal control group, the cell migration rate in 17-AAG alone group was significantly decreased ((10.7±2.7)%, P<0.01), while the cell migration rate in negative pressure treatment alone group was significantly increased ((61.9±2.4)%, P<0.01). Compared with those in 17-AAG alone group, the cell migration rate in 17-AAG+negative pressure treatment group was significantly increased ((37.7±3.7)%, P<0.01). Compared with that in negative pressure treatment alone group, the cell migration rate in 17-AAG+negative pressure treatment group was significantly decreased (P<0.01). At culture hour of 6 after the treatment, compared with those in normal control group, the total length of the tube formed by the cells in 17-AAG alone group was significantly shortened (P<0.05) and the number of branch nodes was significantly reduced (P<0.05), while the total length of the tube formed by the cells in negative pressure treatment alone group was significantly prolonged (P<0.01) and the number of branch nodes was dramatically increased (P<0.01). Compared with that in 17-AAG alone group, the number of branch nodes of the tube formed by the cells was significantly increased in 17-AAG+negative pressure treatment group (P<0.05). Compared with those in negative pressure treatment alone group, the total length of the tube formed by the cells in 17-AAG+negative pressure treatment group was significantly shortened (P<0.01) and the number of branch nodes was significantly reduced (P<0.01). Western blotting detection showed that after treatment, the overall comparison of eNOS and caveolin 1 protein expressions among the three groups of cells showed no statistically significant differences (P>0.05). The expression of HSP90 protein and the eNOS phosphorylation site 1177/eNOS ratio in the cells of negative pressure treatment alone group were significantly increased (P<0.01) compared with those in normal control group. Compared with those in negative pressure treatment alone group, the HSP90 protein expression and the eNOS phosphorylation site 1177/eNOS ratio in the cells of 17-AAG+negative pressure treatment group were significantly decreased (P<0.01). Co-immunoprecipitation and Western blotting detection after the treatment showed that compared with those in normal control group, the expression of caveolin 1 protein in the cells of negative pressure treatment alone group was significantly increased (P<0.01), while the protein expression of eNOS was significantly decreased (P<0.05). Compared with those in negative pressure treatment alone group, the expression of caveolin 1 protein in the cells of 17-AAG+negative pressure treatment group was significantly decreased (P<0.01), while the protein expression of eNOS was significantly increased (P<0.01). After the treatment, compared with those in normal control group, the co-localization of HSP90 and caveolin 1 protein in the cells of negative pressure treatment alone group was significantly increased, while the co-localization of caveolin 1 and eNOS protein was significantly decreased. Compared with those in negative pressure treatment alone group, the co-localization of HSP90 and caveolin 1 protein in the cells of 17-AAG+negative pressure treatment group was significantly decreased, while the co-localization of caveolin 1 and eNOS protein was significantly increased. Molecular docking prediction suggested that caveolin 1 interacted strongly with eNOS and inhibited the 1177 site phosphorylation of eNOS. Conclusions: The negative pressure microenvironment may inhibit the binding of caveolin 1 to eNOS by promoting the binding of HSP90 to caveolin 1 in HUVECs, so as to relieve the inhibition of 1177 site phosphorylation of eNOS by caveolin 1, thereby promoting the proliferation, migration, and tubulogenesis of HUVECs, and ultimately promoting the neogenesis of HUVECs.

Down-regulation of Treg by interference of enhances the killing effect of CIK on leukemia cell HL-60.

OBJECTIVE: Cytokine-induced killer cells (CIK) is a type of immune cell with antitumor activity induced by a variety of cytokines. Regulatory T cells (Treg) is a T cell subgroup featured as immunosuppressive function. Existing CIK cultivation system may inevitably induce Treg. Forkhead box protein 3 (Foxp3) is an essential transcription factor for Treg function. This study aimed to investigate the effects of CIK on the leukemia cell HL-60. MATERIALS AND METHODS: This work silenced Foxp3 expression on the basis of CIK induction, aiming to investigate its killing effect on HL-60 cells. Peripheral blood mononuclear cells were separated and differentiated to CIK in vitro. CD3+CD56+ and CD4+CD25+Foxp3+ Treg cells were detected by flow cytometry. CIK cells were co-cultured with HL-60 cells under the effector-target ratio at 20:1, 10:1, and 5:1, respectively. The killing activity of CIK on HL-60 cells was determined by CCK-8 assay. RESULTS: The ratio of CD3+, CD3+CD8+, and CD3+CD56+ cells gradually increased during CIK induction. Foxp3 interference significantly reduced Treg cell ratio on the 7th day (p < 0.05). Treg cell ratio was significantly lower in Foxp3 interference group at 1.62% ± 0.07% compared with control (p < 0.05). The killing activity of CIK on HL-60 cells enhanced following the increase of effector-target ratio. Interference of Foxp3 significantly elevated the killing activity of CIK on HL-60 cells with effector-target ratio dependence (p < 0.05). CIK can effectively suppress HL-60 cell growth. Treg significantly inhibited the anti-tumor effect of CIK. CONCLUSIONS: Interference of Foxp3 expression significantly declined Treg level and attenuated its suppression impact on CIK, thus enhancing the killing effect of CIK on HL-60 cells.

Crystals of alpha-momorcharin. A new ribosome-inactivating protein.

Crystals of alpha-momorcharin were obtained by vapour phase diffusion. The crystal belongs to the space group R3, with unit cell constants a = b = 131.3 A, c = 39.5 A. There is one alpha-momorcharin molecule in the asymmetric unit; a data set at 3 A has been collected.

Effects of high-intensity treadmill training on timeliness and plasticity expression of irisin in mice.

OBJECTIVE: The purpose of this study was to investigate effects of high-intensity aerobic exercise training on timeliness and plasticity expression of irisin in mice and change of FNDC5, ACCß expression, and to explore possible ways to influence its mechanism of fatty acid metabolism. MATERIALS AND METHODS: Adult male mice of specific pathogen-free grade [Kunming mice, (20 ± 2) g] are randomly divided into 4 groups. Wherein the first group is immediately after one-time exercise groups: including control group (CN group 1), 0.5 h exercise group (group 2), 1 h exercise group (group 3), 1.5 h exercise group (group 4) and 2 h exercise group (group 5), each for 10. The second group is rest after one-time 60 min exercise groups: including control group (CN group 1), rest 20 min groups (groups 2), rest 40 min group (group 3), rest 60 min group (groups 4), rest 80 min group (group 5), each for 10. Third group is immediately after long-term exercise groups: including the control group (CN group 1), 0.5 h exercise group (group 2), 1 h exercise group (group 3), 1.5 h exercise group (group 4) and 2 h exercise group (group 5), each for 10. The fourth group is rest after long-term 60 min exercise group: including control group (CN group 1), rest 20 min group (group 2), rest 40 min group (group 3), rest 60 min group (4 groups) and rest 80 min groups (5 groups), each for 10. RESULTS: With the extension of a one-time high-intensity exercise time, the mouse FNDC5 protein, P-ACCß / ACCß ratio showed fluctuations, and opposite trends between the two, its turning points are 1.5 h; FNDC5 protein and P-ACCß / ACCß ratio with long-term exercise in mice at different time produce adaptability; the regulation of exercise induced irisin timeliness and plasticity reflected after a long-term exercise irisin expression in serum showed a steady decline in trend and return to normal levels, compared to a one-time exercise, expression of irisin is more stable. CONCLUSIONS: With the high-intensity exercise a one-time extension of time, the mouse FNDC5 proteins, P-ACCß / ACCß ratio showed fluctuations, and both changes in the opposite trend, its turning points are 1.5 h; the long-term exercise can produce FNDC5 proteins, P-ACCß / ACCß ratios adaptable, more stable expression of the irisin curve after long-term exercise compared to a one-time exercise.

Role of TYR70 in the N-glycosidase activity of neo-trichosanthin.

Trichosanthin (TCS) is a type I ribosome-inactivating protein (RIP) which possesses rRNA N-glycosidase activity. TCS has long been used as an abortifacient in China. In recent years, its immunomodulatory, anti-tumor and anti-HIV properties have attracted more and more attention. An isoform of trichosanthin, neo-trichosanthin (n-TCS), has been cloned and expressed as recombinant protein. The biochemical studies revealed that n-TCS has virtually the same rRNA N-glycosidase activity as TCS. The crystal structure of n-TCS is similar to TCS. The crystal of Y70A n-TCS, the mutant of recombinant n-TCS, was soaked in sodium citrate buffer (pH 5.5) containing 25% KCl and AMP (10 mg/ml) prior to data collection. After structure determination and refinement, no electron density corresponding to adenine can be detected around the active pocket. Furthermore, the reaction products of Y70A n-TCS and AMP incubated at various reaction times were analyzed using HPLC. No adenine can be detected. These results suggest that Tyr70 is crucial to n-TCS for its substrate recognition, binding and perhaps N-glycosidase activity.

Refined structure of trichosanthin at 1.73 A resolution.

An X-ray reflection data set of the orthorhombic crystal of Trichosanthin (TCS) at 1.73 A resolution had been collected using the area detector. We determined TCS crystal structure by the molecular replacement method using the data of the known alpha-momocharin model and TCS intensities, and then TCS structure refinement at 1.73 A resolution was performed with the restrained least-squares refinement. A final R-factor of 0.186 was obtained with a model obeying standard geometry within 0.013 A in bond lengths and 2.48 degrees in bond angles. The final model contains 133 solvent molecules in the asymmetric unit. This paper gives a detailed description of TCS molecule structure, temperature factors, hydrogen bonds, bound water, the distribution of conserved residues and the interactions between the TCS molecules. The hydrogen bond between the hydroxyl group of conserved residue 14Tyr and O157 plays an important role in maintaining the active site conformation. Conserved residue 160Glu and its conformation at the active site play a key role in the catalytic activity.

Modeling of the three-dimensional structure of luffin-alpha and its simulated reaction with the substrate oligoribonucleotide GAGA.

A fundamental problem in biochemistry and molecular biology is understanding the spatial structure of macromolecules and then analyzing their functions. In this study, the three-dimensional structure of a ribosome-inactivating protein luffin-alpha was predicted using a neural network method and molecular dynamics simulation. A feedforward neural network with the backpropagation learning algorithm were trained on model class of homologous proteins including trichosanthin and alpha-momorcharin. The distance constraints for the C alpha atoms in the protein backbone were utilized to generate a folded crude conformation of luffin-alpha by model building and the steepest descent minimization approach. The crude conformation was refined by molecular dynamics techniques and a simulated annealing procedure. The interaction between luffin-alpha and its analogous substrate GAGA was also simulated to understand its action mechanism.

Studies on derivatives of 2,3-dihydro-4H-1,3,2-benzoxazaphosphorine. Synthesis and structure analysis of 2,3-disubstituted-2,3-dihydro-4H-1,3,2-benzoxazaphosphorin-4-one -(thio ne)-2-sulfide(oxide).

A series of novel organocyclophosphorus compounds including twenty-three 2,3-disubstituted-2,3-dihydro-4H-1,3,2-benzoxazaphosphorin-4-one-2 -sulfide (compounds I) and three 2,3-disubstituted-2,3-dihydro-4H-1,3,2-benzoxazaphosphorin-4-th ion e-2-oxide (compounds II) have been synthesized. Their structures were determined by IR, UV, 1HNMR, X-ray diffraction and elemental analysis. Each of compounds I showed a strong absorption between 1290-1319 cm-1 in the IR spectrum. Comprehensive studies of the spectral data and experimental results indicated that this strong characteristic absorption is different from that of the P = O linkage and thus could be considered as a result of the stretching vibration of (unsaturated C)-N single bond. In the course of synthesis of the compounds, an abnormal product (Formula: see text) is frequently formed as an isomer of the expected product I (Formula: see text). However, by suitable choice of condensation conditions, either of the isomers could be made predominantly in yield and be readily isolated from the other by recrystallizing for several times from appropriate solvent. Data for the melting point, IR, UV and 1HNMR spectra of three pairs of the isomers are given, and primary analyses of the spectra are made as well.

Structure of a phage 434 Cro/DNA complex.

Comparison of the crystal structure of a complex of the phage 434 Cro protein and a synthetic DNA operator with the complex of the same operator and the 434 repressor DNA-binding domain shows different DNA conformations in the two structures. Binding of the protein determines the precise conformation of the DNA in each case.

Role of Arg163 in the N-glycosidase activity of neo-trichosanthin.

Three mutant crystals of neo-trichosanthin (n-TCS), R163K, R163H and R163Q, were obtained by the hanging drop vapor diffusion method. Structure determination indicated that there are no significant differences between the mutants and n-TCS except in the active pocket. All of them were also soaked in sodium citrate buffer (pH 4. 5) containing 20% KCl and 10 mg/ml AMP. Structure determination suggests that in the active pocket of the crystals of R163K and R163H, parallel to the aromatic ring of Tyr70, each mutant possesses an adenine. The relationship between structure and function is discussed. Biochemical analysis reveals that the mutants R163K and R163H have N-glycosidase activity, while R163Q does not. This suggests that R163 is a crucial residue for the enzyme activity of n-TCS, and its role is providing proton.

Structure/function relationship study of Tyr14 and Arg22 in trichosanthin, a ribosome-inactivating protein.

Amino acids Tyr14 and Arg22 in trichosanthin are residues on helix A1 close to the active-site cleft. They are invariant in various type-I and type-II ribosome-inactivating proteins. In this study, Tyr14 was changed to Phe and Arg22 to Lys and Leu. Modified proteins were purified, and activities compared by assaying their median inhibitory concentration (ID50) on a rabbit-reticulocyte-lysate protein-synthesis system. While the ID50 of wild-type trichosanthin was 0.02 nM, those for [Phe14], [Lys22], [Leu22] and [Phe14, Leu22]trichosanthin were 0.10, 0.03, 0.25 and 0.15 nM, respectively. Therefore, compared with Tyr14, Arg22 appears to play a more important role in trichosanthin. Structural studies on [Leu22]trichosanthin showed that two water molecules occupy the space left by the side chain of Arg22, and hydrogen bonds exist between these water molecules and nearby residues to retain the conformation. The use of intermolecular rather than intramolecular hydrogen bonds may have an adverse effect on stability or folding of the protein and results in a mild decrease in activity.