Integrated influence of sulfide modification on the reactivity of nanoscale zero-valent iron towards decabromodiphenyl ether under an electromagnetic field.

Individual application of sulfide modification and electromagnetic field (EMF) can enhance the reactivity of nanoscale zero-valent iron (nZVI), yet the potential of both in combination is not clear. This work found that the reactivity of nZVI towards decabromodiphenyl ether was significantly enhanced by the combined effect of sulfidation and EMF. The specific reaction rate constant of nZVI increased by 7 to 10 times. A series of characterization results revealed that the sulfidation level not only affects the inherent reactivity but also the magnetic-induced heating (MIH) and corrosion (MIC) of nZVI. These collectively influence the degradation efficiency of nZVI under EMF. Sulfidation generally diminished the MIH effect. The low degree of sulfidation (S/Fe = 0.1) slightly reduced the MIC effect by 21.4%. However, the high degree of sulfidation (S/Fe = 0.4) led to significantly enhanced MIC effect by 107.1%. For S/Fe = 0.1 and 0.4, the overall enhancement in the reactivity resulting from EMF was alternately dominated by the contributions of MIH and MIC. This work provides valuable insights into the MIH and MIC effects about the sulfidation level of nZVI, which is needed for further exploration and optimization of this combined technology.

Intestinal natural killer/T-cell lymphoma presenting as a pancreatic head space-occupying lesion: A case report.

BACKGROUND: Intestinal natural killer/T-cell lymphoma (NKTCL) is a rare and aggressive non-Hodgkin's lymphoma, and its occurrence is closely related to Epstein-Barr virus infection. In addition, the clinical symptoms of NKTCL are not obvious, and the specific pathogenesis is still uncertain. While NKTCL may occur in any segment of the intestinal tract, its distinct location in the periampullary region, which leads clinicians to consider mimics of a pancreatic head mass, should also be addressed. Therefore, there remain huge challenges in the diagnosis and treatment of intestinal NKTCL. CASE SUMMARY: In this case, we introduce a male who presented to the clinic with edema of both lower limbs, accompanied by diarrhea, and abdominal pain. Endoscopic ultrasound (EUS) showed well-defined homogeneous hypoechoic lesions with abundant blood flow signals and compression signs in the head of the pancreas. Under the guidance of EUS- fine needle biopsy (FNB) with 19 gauge or 22 gauge needles, combined with multicolor flow cytometry immunophenotyping (MFCI) helped us diagnose NKTCL. During treatments, the patient was prescribed the steroid (dexamethasone), methotrexate, ifosfamide, L-asparaginase, and etoposide chemotherapy regimen. Unfortunately, he died of leukopenia and severe septic shock in a local hospital. CONCLUSION: Clinicians should enhance their understanding of NKTCL. Some key factors, including EUS characteristics, the right choice of FNB needle, and combination with MFCI, are crucial for improving the diagnostic rate and reducing the misdiagnosis rate.

Effect of soil pH on thermally enhanced desorption of m-xylene by zero-valent iron particles under an electromagnetic field.

This study, for the first time, evaluates a novel method for the desorption of contaminants from soil that uses the heat generated by zero-valent iron (ZVI) under low-frequency electromagnetic fields (EMF), and elucidates the specific effects of soil pH upon the process. It was found that the temperature of soil mixed with ZVI could reach up to ∼60 °C within 20 min under the applied EMF, and after 60 min the residual fraction of m-xylene in soil decreased by 86.4% compared to no-ZVI soil. The most efficient desorption of m-xylene occurred at a soil of pH 5. Desorption was related to the net heating capacity of the ZVI particles, which was defined by pH-dependent formation of surface corrosion products. The preservation of metal iron and formation of Fe(II) species was favored for heat generation. Soil pH also affected m-xylene retention and the local thermal conduction from ZVI to m-xylene by regulating the surface properties of fulvic acid and ZVI. This study provides valuable information regarding the impact of pH on the thermal desorption of soil contaminants by ZVI coupled with EMF and illustrates the potential of the method in the remediation of contaminated sites.

Colorectal cancer (CRC) as a multifactorial disease and its causal correlations with multiple signaling pathways.

Colorectal cancer (CRC) is the third most common malignancy and one of the leading causes of cancer-related death among men worldwide. CRC is a multifactor digestive pathology, which is a huge problem faced not only by clinicians but also by researchers. Importantly, a unique feature of CRC is the dysregulation of molecular signaling pathways. To date, a series of reviews have indicated that different signaling pathways are disordered and have potential as therapeutic targets in CRC. Nevertheless, an overview of the function and interaction of multiple signaling pathways in CRC is needed. Therefore, we summarized the pathways, biological functions and important interactions involved in CRC. First, we investigated the involvement of signaling pathways, including Wnt, PI3K/Akt, Hedgehog, ErbB, RHOA, Notch, BMP, Hippo, AMPK, NF-κB, MAPK and JNK. Subsequently, we discussed the biological function of these pathways in pathophysiological aspects of CRC, such as proliferation, apoptosis and metastasis. Finally, we summarized important interactions among these pathways in CRC. We believe that the interaction of these pathways could provide new strategies for the treatment of CRC.

[Efficacy and safety of the HAA regimen as induction chemotherapy in 236 de novo acute myeloid leukemia].

OBJECTIVE: To evaluate the efficacy and safety of the HAA regimen (homoharringtonine, cytarabine and aclarubicin) as induction chemotherapy in de novo acute myeloid leukemia (AML). METHODS: The efficacy and safety of 236 de novo AML patients who received the HAA regimen as induction chemotherapy were retrospectively analyzed. The complete remission (CR) rate was assayed. Kaplan-Meier method was used to estimate overall survival (OS) and relapse free survival (RFS), and the differences were compared by Log-rank test. RESULTS: The overall CR rate was 78.0%, and 65.7% of the patients attained CR in the first induction cycle. The early death rate was 4.7%. The median followup time was 41(1-161) months. The estimated 5-year OS and 5-year RFS rates were 44.9% and 45.5%, respectively. The CR rates of patients with favorable, intermediate and unfavorable cytogenetics were 92.9%,78.6%and 41.7%, respectively. The 5-year OS of favorable and intermediate group were 61.1% and 45.1%, respectively. The 5- year RFS of favorable and intermediate group were 49.0% and 45.4%, respectively. The median survival time of unfavorable group was only 5 months. The side effects associated with the HAA regimen were tolerable, in which the most common toxicities were myelosuppression and infection. CONCLUSION: The HAA regimen is associated with a higher rate of CR and longer survival time and its toxicity could be tolerated.

Homoharringtonine-based induction regimens for patients with de-novo acute myeloid leukaemia: a multicentre, open-label, randomised, controlled phase 3 trial.

BACKGROUND: Homoharringtonine-based induction regimens have been widely used in China for patients with acute myeloid leukaemia. However, their efficacy has not been tested in a multicentre randomised controlled trial in a large population. We assessed the efficacy and safety of homoharringtonine-based induction treatment for management of newly diagnosed acute myeloid leukaemia. METHODS: This open-label, randomised, controlled, phase 3 study was done in 17 institutions in China between September, 2007, and July, 2011. Untreated patients aged 14-59 years with acute myeloid leukaemia were randomly assigned (by a computer-generated allocation schedule without stratification) to receive one of three induction regimens in a 1:1:1 ratio: homoharringtonine 2 mg/m(2) per day on days 1-7, cytarabine 100 mg/m(2) per day on days 1-7, and aclarubicin 20 mg/day on days 1-7 (HAA); homoharringtonine 2 mg/m(2) per day on days 1-7, cytarabine 100 mg/m(2) per day on days 1-7, and daunorubicin 40 mg/m(2) per day on days 1-3 (HAD); or daunorubicin 40-45 mg/m(2) per day on days 1-3 and cytarabine 100 mg/m(2) per day on days 1-7 (DA). Patients in complete remission were offered two cycles of intermediate-dose cytarabine (2 g/m(2) every 12 h on days 1-3). The primary endpoints were the proportion of patients who achieved complete remission after two cycles of induction treatment and event-free survival in the intention-to-treat population. The trial is registered in the Chinese Clinical Trial Register, number ChiCTR-TRC-06000054. FINDINGS: We enrolled 620 patients, of whom 609 were included in the intention-to-treat analysis. 150 of 206 patients (73%) in the HAA group achieved complete remission versus 125 of 205 (61%) in the DA group (p=0.0108); 3-year event-free survival was 35.4% (95% CI 28.6-42.2) versus 23.1% (95% CI 17.4-29.3; p=0.0023). 133 of 198 patients (67%) in the HAD group had complete remission (vs DA, p=0·20) and 3-year event-free survival was 32.7% (95% CI 26.1-39.5; vs DA, p=0.08). Adverse events were much the same in all groups, except that more patients in the HAA (12 of 206 [5.8%]) and HAD (13 of 198 [6.6%]) groups died within 30 days than in the DA group (two of 205 [1%]; p=0.0067 vs HAA; p=0.0030 vs HAD). INTERPRETATION: A regimen of homoharringtonine, cytarabine, and aclarubicin is a treatment option for young, newly diagnosed patients with acute myeloid leukaemia. FUNDING: Chinese National High Tech Programme, Key Special Research Foundation of the Ministry of Science and Technology of China, National Nature Science Foundation of China, National Clinical Key Specialty Construction Project.

[Cytotoxicity of homoharringtonine on leukemic stem-like cells in AML cell line KG-1].

OBJECTIVE: To investigate the effect of homoharringtonine (HHT) on leukemic stem-like cells (LSC) in human acute myeloid leukemia (AML) cell lines. METHODS: The phenotypes of AML cell lines U937,Kasumi-1,and KG-1 cells were analyzed by flow cytometry (FACS). The effect of HHT on leukemia stem-like cells with immunophenotype of CD34(+)CD38(-)CD96(+) was detected with FACS. Cell growth was measured by MTT assay. Activation of Caspase pathway and expression of apoptosis-related regulator proteins were examined by Western blotting. RESULTS: FACS demonstrated that the 69% of KG-1 cells expressed LSC phenotype CD34(+)CD38(-)CD96(+), while 26.7% on Kasumi-1 cells expressed this marker. In contrast,U937 cells showed CD96 negative. HHT significantly inhibited cell growth of KG-1 cells with an IC(50) of 16.9 ng/ml at 48 h. The ratio of CD34(+)CD38(-)CD96(+) cells decreased from 63.6% to 17.1% after HHT treatment. Enhanced apoptosis was demonstrated in HHT group evidenced by strong activation of Caspase-9,Caspase-3 and PARP.HHT treatment resulted in down-regulation of expression of anti-apoptotic protein BCL-2 and phosphorylated-Akt. CONCLUSION: HHT can effectively kill the leukemic stem-like cells in human AML cell line KG1 by inhibiting cell growth and inducing apoptosis which is associated with activation of Caspase pathway and down-regulation of anti-apoptotic proteins and phosphorylated-Akt.

[Expression and clinical significance of ID1 gene in acute myeloid leukemia].

OBJECTIVE: To explore the expression and clinical significance of ID1 gene in acute myeloid leukemia (AML) patients. METHOD: Real-time quantitative PCR (RQ-PCR) was used to test the expression level of ID1 gene in 114 de novo adult AML patients, and the clinical features of these patients were analyzed. RESULTS: ID1 gene transcript levels were detectable in BM mononuclear cells from 114 patients with AML, the median expression level of all samples was 8525 (range: 57 - 11 233 238). There was a statistically significant difference on expression level of ID1 gene among the three different cytogenetic prognosis groups, and the poor prognosis group (median: 36 840, range: 336 - 11 233 238) harbored the significantly higher level of ID1 gene than the intermediate prognosis group (Median: 6630, range: 66 - 1 840 798) (P = 0.006). The expression level of ID1 gene was positively associated with older age (age ≥ 60 years vs < 60 years, P = 0.002) and higher WBC count (WBC ≥ 10×10(9)/L vs < 10×10(9)/L, P = 0.005). Young patients (age < 60 years) who were not obtained the complete remission (non-CR) after the first cycle of chemotherapy harbored the high level of ID1 gene (Median: 9537 of non-CR vs 1268 of CR, P = 0.010). CONCLUSIONS: High expression level of ID1 gene was mostly seen in AML patients with adverse cytogenetics and older age (age ≥ 60 years), and may be associated with poor prognosis of AML. ID1 gene might be a prognostic molecular marker of AML.

[Dispersion behavior of effective ingredients in Chinese medicine decoctions].

OBJECTIVE: To research the disperse behavior of many Chinese medicine decoctions. METHODS: Through the analysis of the dispersible attributes of 22 kinds of Chinese medicine decoctions including Radix Salviae Miltiorrhizae by means of turbidity, ultramicroscope and TEM, we found that a lot of nanometer particles existed in these decoctions after 4000 r/min centrifugation. Based on the model of Radix Salviae Miltiorrhizae, we analyzed the influence on the loss of effective ingredients by way of centrifugation, alcohol precipitation, flocculation and salting-out edulcoration. RESULTS: The removal of infinite nanometer particles from these decoctions led to the greater loss of water-soluble and fat-soluble ingredients,and the latter accounts for the major loss. CONCLUSION: Oral liquid preparation of traditional Chinese medicine is a kind of nano-pharmaceutics with nanometer particles dispersed in the water as the carriers of effective ingredients in medicine.

Triptolide inhibits the proliferation of cells from lymphocytic leukemic cell lines in association with downregulation of NF-κB activity and miR-16-1*.

AIM: To examine the effects of triptolide (TPL) on T-cell leukemia cells and identify their underlying mechanisms. METHODS: The cytotoxicity of TPL was assessed by MTT assay. Cell apoptosis was determined using annexin V and DAPI staining and analyzed by flow cytometry or fluorescence microscopy. The activation of caspase pathways and the expression of nuclear factor κB (NF-κB) p65 were examined by Western blotting. Differences in microRNA (miRNA) expression in Molt-4 and Jurkat cells before and after TPL treatment were identified using microarrays and real-time RT-PCR, respectively. RESULTS: TPL 20-160 nmol/L treatment potently inhibited cell growth and induced apoptosis in T-cell lymphocytic leukemia cell lines. Molt-4 and Jurkat cells, however, were more sensitive to TPL than L428 and Raji cells. After 24 h of treatment, bortezomib abrogated the growth of Molt-4 and Jurkat cells with an IC(50) of 15.25 and 24.68 nmol/L, respectively. Using Molt-4 cells, we demonstrated that treatment 20-80 nmol/L inhibited the translocation of NF-κB p65 from the cytoplasm to the nucleus and that phosphorylated NF-κB p65 in nuclear extracts was down-regulated in a dose-dependent manner. Similar results were also seen in Jurkat cells but not in L428 cells, as these cells are resistant to TPL and bortezomib (a NF-κB inhibitor). Twenty-three miRNAs were differentially expressed after TPL treatment. Functional analysis revealed that TPL treatment could inhibit expression of miR-16-1* and that transfection of miR-16-1* led to significantly decreased apoptosis induced by TPL. CONCLUSION: Our in vitro studies suggest that TPL might be an effective therapeutic agent for treatment of T-cell lymphocytic leukemia and that its cytotoxic effects could be associated with inhibition of NF-κB and down-regulation of miR-16-1*.

[Clinical study of Philadelphia chromosome-positive adult acute lymphoblastic leukemia].

OBJECTIVE: To study the clinical characteristics, risk factors and therapeutic outcome of Philadelphia chromosome-positive adult acute lymphoblastic leukemia (Ph(+)aALL). METHODS: The clinical data of 117 newly diagnosed adults with Ph(+)ALL in our hospital between January 1995 and December 2009 were retrospectively analyzed. And their prognoses were followed up. RESULTS: There were 117(16.1%) of 727 aALL patients diagnosed as Ph(+)aALL. Among the 117 cases, 64.1% patients were classified as pre-B immunophenotype and 31.3% as common B immunophenotype, 37.5% patients with co-expression of myeloid antigens (CD13 or CD33), and 98.4% patients with positive CD34. The complete remission (CR) rate after 1 or 2 cycles of induction chemotherapy was 62.2% in Ph(+)aALL group versus 82% in Ph(-)aALL group (P = 0.000). The median disease-free survival time of Ph(+) group was 6 months and the median survival time was 9 months. Sole karyotype abnormality subgroup t(9;22) accounted for 53% of all Ph(+)aALL patients and additional karyotype abnormality subgroup, t(9;22) plus other chromosome variation, accounted for 47%. Patients in sole karyotype abnormality subgroup had slightly lower CR rate (59.6% vs 62.5%, P = 0.768), longer median survival time (7 months vs 4 months, P = 0.158), and higher 3-year overall survival rate (27.3% vs 14.4%, P = 0.271). For the myeloid antigen co-expressed patients and the only lymphocytic antigen expressed ones, CR rate was 56.0% and 61.5% (P = 0.750), the median survival time was 5 months and 4 months (P = 0.182), and the 3-year overall survival rate was 16.0% and 15.0% (P = 0.354), respectively. In the imatinib plus combination chemotherapy treatment group, 81.3% patients achieved CR, compared with that of 58.3% in patients treated with only traditional combination chemotherapy (P = 0.083). The median survival time was 9.5 months and 6 months (P = 0.003) in these two subgroup, and 3-year overall survival rate was 52.2% and 10.3% (P = 0.029), respectively. For the patients receiving allo-HSCT after CR and that receiving traditional consolidation chemotherapy, the median survival time was 15 months and 6 months (P = 0.000), and the 3-year overall survival rate was 62.0% and 10.3% (P = 0.000), respectively. For the patients receiving imatinib as consolidation-maintenance treatment and that receiving allo-HSCT, the median survival time was 12 months and 15 months (P = 0.300), and the 3-year overall survival rate was 64.7% and 62% (P = 0.505), respectively. CONCLUSION: Of all adult ALL patients, the Ph(+) subgroup accounted for about 16.1%, which have unfavorable prognosis such as lower CR rate and shorter survival duration under traditional chemotherapy. Neither additional chromosome abnormalities to t(9;22) nor co-expression of myeloid antigen had negative effect on CR rate and survival duration. Addition of imatinib to the therapy was beneficial to improve the CR rate and survival duration. Either receiving imatinib as consolidation-maintenance treatment or allo-HSCT after complete remission can improve long-term survival rate of Ph(+) adult ALL group significantly.

Screening, characterization, and cloning of a solvent-tolerant protease from Serratia marcescens MH6.

A solvent-tolerant bacterium strain MH6 was isolated by hydrophilic organic solvent DMSO enrichment in medium and identified as Serratia marcescens. The extracellular protease with novel organic-solvent-stable properties from strain MH6 was purified and characterized. The molecular weight of the purified protease was estimated to be 52 kDa on SDS-PAGE. The open reading frame (ORF) of the MH6 protease encoded 504 amino acids with 471 amino acid residues in the mature protease. Based on the inhibitory effects of EDTA and 1, 10-phenathroline, the MH6 protease was characterized as a metalloproteinase. The enzyme activity was increased in the presence of Ni2+, Mg2+, and Ca2+. The protease could also be activated by the nonionic surfactants Tween 80 (1.0%) and Triton X-100 (1.0%). The protease showed remarkable solvent stability in the presence of 50% (v/v) solutions of long-chain alkanes and long-chain alcohols. It was also fairly stable in the presence of 25% solutions of hydrophilic organic solvents. Due to its high stability in solvents and surfactants, the MH6 protease is an ideal candidate for applications in organic catalysis and other related fields.

[Cytogenetic analysis of 154 case of acute myeloid leukemia with t(8;21)].

OBJECTIVE: To investigate the cytogenetic features of acute myeloid leukemia (AML) with t(8;21). METHODS: The clinical characteristics of 154 cases of acute myeloid leukemia with t(8;21) in our hospital were analyzed retrospectively. According to the chromosome karyotype, all cases were divided into three groups: the group without additional chromosome abnormality, the group with single sex chromosome loss and the group with additional chromosome abnormalities other than sex chromosome loss. RESULT: In this study, according to FAB classification, there were 127 cases of M2 (82.5%), 15 of M5 (9.7%), 6 of M4 (3.9%), 4 of M1(2.6%) and 2 of M0(1.3%). Cytogenetically, 85 (55.2%) AML patients with t(8;21) had additional chromosome abnormalities. The most common abnormalities were sex chromosome loss, of which -Y was detected in 44.1% of the male karyotype and X in 27.9%. Beside that, there were 9 cases of 9q- (5.8%), 5 of +8(3.3%),3 of +4(2.0%) and 17 of other chromosome anomalies (11.4%). In the group of t(8;21) with additional chromosome abnormalities, 11 cases (35.5%) were non-M2 AML, higher than that in single t(8;21) group (17.4%)(P<0.05); however, there was no significant difference between the group of single t(8;21) and the group of t(8;21) with single sex chromosome loss(P>0.05). CONCLUSION: t(8;21) translocation is usually accompanied by additional chromosome abnormalities, particularly in M2; while t(8;21) with additional chromosome abnormalities other than sex chromosome loss is more frequently observed in non-M2 AML.

Synthesis and discovery of a novel pyrazole derivative as an inhibitor of apoptosis through modulating integrin beta4, ROS, and p53 levels in vascular endothelial cells.

Recently, pyrazole derivatives as high affinity and selective A2A adenosine receptor antagonists have been reported. But, so far, there are no reports about the inhibitory effects of multi-substituted pyrazole derivatives on apoptosis of vascular endothelial cells (VECs). In this study, we synthesized six pyrazole derivatives and characterized the structures of the compounds by IR, (1)H NMR, mass spectroscopy, and element analysis. The biology assay showed that a novel pyrazole derivative, ethyl 3-(o-chlorophenyl)-5-methyl-1-phenyl-1H-pyrazole-4-carboxylate (MPD) at low concentration (25muM) increased VECs viability and inhibited VECs apoptosis induced by deprivation of serum and FGF-2. During this process, the levels of integrin beta4, reactive oxygen species (ROS), and p53 were depressed obviously. The data suggested that MPD was a potential inhibitor of apoptosis associated with the signal pathway mediated by integrin beta4, ROS, and p53 in VECs.

Design, synthesis, and preliminary biological evaluation of 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives.

We synthesized a series of novel small molecules, 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives, by tandem reduction-oxirane opening of 2-nitroaroxymethyloxiranes in moderate or excellent yields. We investigated the effects of all of the compounds on HUVEC apoptosis and A549 cell growth. The results showed that 6,8-dichloro-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine was the most effective small molecule in promoting HUVEC apoptosis and inhibiting A549 cell proliferation, but 6-amino-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine could remarkably inhibit HUVEC apoptosis and might induce the formation of microvessel.

Crystal structure of human coactosin-like protein.

Human coactosin-like protein is an actin filament binding protein but does not bind to globular actin. It associates with 5-Lipoxygenase both in vivo and in vitro, playing important roles in modulating the activities of actin and 5-Lipoxygenase. Coactosin counteracts the capping activity of capping protein which inhibits the actin polymerization. We determined the crystal structures of human coactosin-like protein by multi-wavelength anomalous dispersion method. The structure showed a high level of similarity to ADF-H domain, although their amino acid sequences share low degree of homology. A few conserved hydrophobic residues that may contribute to the folding were identified. This structure suggests coactosin-like protein bind to F-actin in a different way from ADF/Cofilin family. Combined with the information from previous mutagenesis studies, the binding sites for F-actin and 5-Lipoxygenase were analyzed, respectively. These two sites are quite close, which might prevent F-actin and 5-Lipoxygenase from binding to coactosin simultaneously.

Cloning, purification, crystallization and preliminary crystallographic analysis of human phosphoglycerate mutase.

Human B-type 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase (dPGM-B) has been cloned, overexpressed and purified, with a yield of 30% of the total protein. Crystals of human dPGM-B were obtained using the hanging-drop vapour-diffusion technique. X-ray diffraction data were collected to 2.8 A resolution. The human dPGM-B crystals belong to space group P2(1), with unit-cell parameters a = 130.5, b = 75.9, c = 187.0 A, beta = 94.4 degrees. There could be between 9 and 18 monomers per asymmetric unit, with 12 molecules being the most likely.

Expression, purification and preliminary crystallographic studies of human coactosin-like protein.

Coactosin-like protein (CLP) is an actin-binding protein as well as a 5-lipoxygenase binding partner. Human coactosin-like protein has been expressed in high yield and the His-tagged protein was purified by affinity chromatography. Several different crystal forms were obtained by the hanging-drop vapour-diffusion method. X-ray diffraction data to 2.0 A resolution were collected from the best crystal. The space group was determined to be P2(1)2(1)2(1), with unit-cell parameters a = 38.4, b = 48.7, c = 72.6 A.

Crystal structure of human bisphosphoglycerate mutase.

Bisphosphoglycerate mutase is a trifunctional enzyme of which the main function is to synthesize 2,3-bisphosphoglycerate, the allosteric effector of hemoglobin. The gene coding for bisphosphoglycerate mutase from the human cDNA library was cloned and expressed in Escherichia coli. The protein crystals were obtained and diffract to 2.5 A and produced the first crystal structure of bisphosphoglycerate mutase. The model was refined to a crystallographic R-factor of 0.200 and R(free) of 0.266 with excellent stereochemistry. The enzyme remains a dimer in the crystal. The overall structure of the enzyme resembles that of the cofactor-dependent phosphoglycerate mutase except the regions of 13-21, 98-117, 127-151, and the C-terminal tail. The conformational changes in the backbone and the side chains of some residues reveal the structural basis for the different activities between phosphoglycerate mutase and bisphosphoglycerate mutase. The bisphosphoglycerate mutase-specific residue Gly-14 may cause the most important conformational changes, which makes the side chain of Glu-13 orient toward the active site. The positions of Glu-13 and Phe-22 prevent 2,3-bisphosphoglycerate from binding in the way proposed previously. In addition, the side chain of Glu-13 would affect the Glu-89 protonation ability responsible for the low mutase activity. Other structural variations, which could be connected with functional differences, are also discussed.