Biomedical subjects

L Feng

Publications and source records attributed to L Feng.

At least 91 records · Page 5Linked to original sources

PubMed2000

Loss control of Mcm5 interaction with chromatin in cdc6-1 mutated in CDC-NTP motif.

Saccharomyces cerevisiae Cdc6 plays an essential role in establishing and maintaining the prereplicative complex (pre-RC) by interacting with the origin recognition complex (ORC) and associating with chromatin origins. These interactions are required to load minichromosome maintenance proteins (MCMs) and other initiator proteins onto replication origins. Although the temperature-sensitive cdc6 mutant, cdc6-1, has been widely used for these studies, the molecular mechanism of the cdc6-1 mutation has been unclear. In this study, we have identified a base substitution at Gly260-->Asp, near the CDC-NTP motif. Using a chromatin immunoprecipitation assay (CHIP), we found that cdc6-1 fails to load Mcm5 onto the replication origins. Chromatin fractions were used to study Mcm5 binding in both the wildtype and mutant background. These studies indicated that Cdc6 is also involved in unloading Mcm5 from chromatin. Specifically, the cdc6-1 mutation protein, cdc6(G260D), which failed to load Mcm5 onto replication origins, also failed to unload the Mcm5 protein. Furthermore, the overexpression of wildtype CDC6 accelerated the unloading of Mcm5 from chromatin fractions. In the absence of functional Cdc6, the Mcm5 protein showed nonorigin binding to chromatin with the cell cycle arrested at the G1S phase transition. Our results suggested that the cdc6(G260D) mutant protein fails to assemble an operational replicative complex and that wildtype Cdc6 plays a role in preventing re-replication by controlling the unloading the MCMs from chromatin origins.

Amino Acid Substitution↗

PubMed2000

Identification and characterization of Saccharomyces cerevisiae Cdc6 DNA-binding properties.

Recent studies have shown that Cdc6 is an essential regulator in the formation of DNA replication complexes. However, the biochemical nature of the Cdc6 molecule is still largely unknown. In this report, we present evidence that the Saccharomyces cerevisiae Cdc6 protein is a double-stranded DNA-binding protein. First, we have demonstrated that the purified yeast Cdc6 can bind to double-stranded DNA (dissociation constant approximately 1 x 10(-7) M), not to single-stranded DNA, and that the Cdc6 molecule is a homodimer in its native form. Second, we show that GST-Cdc6 fusion proteins expressed in Escherichia coli bind DNA in an electrophoretic mobility shift assay. Cdc6 antibodies and GST antibodies, but not preimmune serum, induce supershifts of GST-Cdc6 and DNA complexes in these assays, which also showed that GST-Cdc6 binds to various DNA probes without apparent sequence specificity. Third, the minimal requirement for the binding of Cdc6 to DNA has been mapped within its N-terminal 47-amino acid sequence (the NP6 region). This minimal binding domain shows identical DNA-binding properties to those possessed by full-length Cdc6. Fourth, the GST-NP6 protein competes for DNA binding with distamycin A, an antibiotic that chelates DNA within the minor groove of the A+T-rich region. Finally, site-direct mutagenesis studies revealed that the (29)KRKK region of Cdc6 is essential for Cdc6 DNA-binding activity. To further elucidate the function of Cdc6 DNA binding in vivo, we demonstrated that a binding mutant of Cdc6 fails to complement either cdc6-1 temperature-sensitive mutant cells or Deltacdc6 null mutant cells at the nonpermissive temperature. The mutant gene also conferred growth impairments and increased the plasmid loss in its host, indicative of defects in DNA synthesis. Because the mutant defective in DNA binding also fails to stimulate Abf1 ARS1 DNA-binding activity, our results suggest that Cdc6 DNA-binding activity may play a pivotal role in the initiation of DNA replication.

Binding Sites↗

PubMed2000

Abnormal pattern of Tie-2 and vascular endothelial growth factor receptor expression in human cerebral arteriovenous malformations.

OBJECTIVE: Human cerebral arteriovenous malformations (AVMs) are speculated to result from abnormal angiogenesis. Vascular endothelial growth factor receptors (VEGF-Rs) and Tie-2 play critical roles in vasculogenesis and angiogenesis. We hypothesized that the abnormal vascular phenotype of AVMs may be associated with abnormal expression of VEGF-Rs and Tie-2. METHODS: We measured the expression of Tie-2, VEGF-R1, and VEGF-R2 in AVMs and normal brain tissue, using immunoblotting. To assess active vascular remodeling, we also measured endothelial nitric oxide synthase expression. CD31 expression was used to control for endothelial cell mass for Tie-2, VEGF-Rs, and endothelial nitric oxide synthase. Immunoblotting data were presented as relative expression, using normal brain tissue values as 100%. RESULTS: CD31 was expressed to similar degrees in AVMs and normal brain tissue (99+/-29% versus 100+/-20%, mean +/- standard error, P = 0.98). Tie-2 expression was markedly decreased in all AVMs, compared with normal brain tissue (16+/-9% versus 100+/-37%, P = 0.04). VEGF-R1 expression was decreased in four of five AVMs, but the difference between the mean values was not significant (35+/-8% versus 100+/-42%, P = 0.14). VEGF-R2 expression was decreased in all AVMs, compared with normal brain tissue (28+/-6% versus 100+/-29%, P = 0.03). There was no difference in endothelial nitric oxide synthase expression between AVMs and normal brain tissue (106+/-42% versus 100+/-25%, P = 0.91). CONCLUSION: AVM vessels exhibited abnormal expression of Tie-2 and VEGF-Rs, both of which may contribute to the pathogenesis of AVMs.

Adult↗

PubMed2000

Cytokine and adhesion molecule expression in SCID mice reconstituted with CD4+ T cells.

The objectives of this study were to quantify colonic cytokine and endothelial cell adhesion molecule (ECAM) expression in the colons of severe combined immunodeficient (SCID) mice reconstituted with different subsets of CD4+ T lymphocytes. We found that animals injected with CD45RBhigh but not CD45RBlow T cells or phosphate-buffered saline (PBS) developed clinical evidence of colitis at 6-8 weeks following reconstitution, as assessed by loss of body weight, development of loose stools and/or diarrhea, and histopathology. Concurrent with the onset of distal bowel inflammation was enhanced expression of a variety of Th1 and macrophage-derived cytokines including interferon gamma, tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-12, and IL-18 lymphotoxin-beta. In addition, message levels and vascular surface expression of ICAM-1, VCAM-1, and MAdCAM-1 were all significantly enhanced in the colitic SCID mice reconstituted with CD45RBhigh T cells compared with SCID mice reconstituted with PBS or CD45RBlow T cells that did not develop disease. Significant increases in some of these ECAMs were also noted in the cecum and stomach and to a lesser degree in the small bowel. Our data confirm that reconstitution of SCID mice with CD45RBhigh but not CD45RBlow T cells induces chronic colitis, and that the colonic inflammation is associated with enhanced expression of proinflammatory cytokines and different ECAMs in the colon. Furthermore, our studies demonstrate that reconstitution of SCID mice with CD45RBhigh T cells enhances ECAM expression in tissues distant from the site of active inflammation.

Animals↗

PubMed2000

Conditions for electron capture by an ultraintense stationary laser beam

We present in this paper a quantitative study of an effect, in which a low-energy free electron is captured and violently accelerated to GeV final kinetic energy by a stationary extra-high-intensity laser beam (Q0 identical witheE/m(e)omegac greater, similar100). The conditions under which this phenomenon can occur, such as the momentum range, incident angle of the incoming electron, the waist width of the laser beam, etc., have been investigated in detail.

Journal Article↗

PubMed2000

Glomerular extracellular matrix accumulation in experimental anti-GBM Ab glomerulonephritis.

Thickening of the glomerular basement membrane (GBM) results from excessive accumulation of extracellular matrix (ECM) proteins following glomerular injury. We studied the temporal relationship between the expression of growth factors, ECM accumulation, ECM degrading proteinases, and their inhibitors in a rat model of anti-GBM antibody (Ab) glomerulonephritis (GN) by the RNase protection assay and immunohistochemistry. There were two- or fourfold increases in the expression of transforming growth factor-beta(1) (TGF-beta(1)) and platelet-derived growth factor (PDGF) A and B chain mRNAs 4 days after anti-GBM Ab administration. These changes were temporally associated with increased accumulation of alpha1(III) and alpha2(IV) collagens, fibronectin, and heparan sulfate proteoglycan along the GBM. The increase in matrix accumulation was associated with little or no increases in the proteinases, urokinase plasminogen activator (u-PA) and transin, respectively. There was a 1.6x increase in the u-PA/28s mRNA ratio on day 4 in rats with anti-GBM Ab GN, but this was not associated with an increase in u-PA biologic activity. By comparison, the mRNAs of the proteinase inhibitors, plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of metalloproteinase (TIMP) were 5x greater than that of control rats on day 4. PAI-1 mRNA correlate with increased biologic activity. These data demonstrate a temporal association between TGF-beta(1) and PDGF expression and matrix accumulation within the GBM in anti-GBM Ab GN. In addition, it suggest that this matrix accumulation results from an imbalance between matrix synthesis and degradation.

Animals↗

PubMed2000

Surface photo-grafting of polyurethane with 2-hydroxyethyl acrylate for promotion of human endothelial cell adhesion and growth.

Cytocompatible polyurethane (PU) surface was prepared by photo-grafting 2-hydroxyethyl acrylate (HEA) onto the membrane surface. Graft polymerization was conducted by combining the use of the photo-oxidation and irradiation grafting. PU membrane was photo-oxidized to introduce the hydroperoxide groups onto the surface, then the membrane, immersed previously in monomer solution, was irradiated under UV light. The ATR-FTIR spectra, element spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM) and water contact angle characterized the grafted copolymers and verified the occurrence of graft polymerization. The results showed that UV irradiation could realize the graft polymerization effectively and the grafting was confined within the surface layer. The grafted membrane showed minimal surface morphology. Human umbilical vein endothelial (HUVE) cells were seeded on the grafted surface. The performance of the surface in cell attachment and growth correlated with the oxygen content and mainly the carbonyl content on the surface. Cells were spread more extensively and grew faster on the surface with a higher oxygen content.

Acrylates↗

PubMed2000

Heparin-binding EGF-like growth factor contributes to reduced glomerular filtration rate during glomerulonephritis in rats.

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family, is expressed during inflammatory and pathological conditions. We have cloned the rat HB-EGF and followed the expression of HB-EGF in rat kidneys treated with anti- glomerular basement membrane (anti-GBM) antibody (Ab) to induce glomerulonephritis (GN). We observed glomerular HB-EGF mRNA and protein within 30 minutes of Ab administration and showed by in situ hybridization that glomerular HB-EGF mRNA expression was predominantly in mesangial and epithelial cells. Expression of HB-EGF correlated with the onset of decreased renal function in this model. To test the direct effect of HB-EGF on renal function, we infused the renal cortex with active rHB-EGF, prepared from transfected Drosophila melanogaster cells. This treatment induced a significant decrease in single nephron GFR (SNGFR), single nephron plasma flow, and glomerular ultrafiltration coefficient and an increase in the glomerular capillary hydrostatic pressure gradient. In addition, anti-HB-EGF Ab administered just before anti-GBM Ab blocked the fall in SNGFR and GFR at 90 minutes without any change in the glomerular histologic response. These studies suggest that HB-EGF expressed early in the anti-GBM Ab GN model contributes to the observed acute glomerular hemodynamic alterations.

Animals↗

PubMed2000

Retinoic acid receptor-beta as a prognostic indicator in stage I non-small-cell lung cancer.

PURPOSE: Retinoids are pivotal in the growth and differentiation of certain epithelial tissues, interacting with nuclear retinoid receptors (the retinoic acid receptors [RARs] and retinoid X receptors [RXRs]), which function as transcription factors. RAR-beta mRNA is undetectable by in situ hybridization (ISH) in 50% of non-small-cell lung cancers (NSCLC). RAR-beta may suppress tumorigenicity. Therefore, we hypothesized that loss of expression of RAR-beta gene in stage I NSCLC is a prognostic factor of a poor clinical outcome. PATIENTS AND METHODS: We retrospectively analyzed RAR-beta mRNA levels (by ISH using a digoxigenin-labeled antisense riboprobe) in specimens from 185 consecutive patients with completely resected clinical/radiographic stage I NSCLC for whom clinical follow-up data were available. RESULTS: One hundred fifty-six patients who met the criteria of pathologic stage I NSCLC and positivity for RXR-alpha mRNA (used as a control to assess RNA degradation) and who had adequate follow-up could be evaluated. RAR-beta mRNA expression was undetectable in 51 patients, weakly positive in 64 patients, and strongly positive in 41 patients. Overall survival of the 41 patients with strongly positive RAR-beta was significantly worse than for the 115 patients with weak or absent RAR-beta (P =.045). CONCLUSION: Unexpectedly, strong RAR-beta expression was associated with a significantly worse outcome of early-stage NSCLC. The mechanisms underlying this clinically and biologically important finding should be further explored.

Adult↗

PubMed2000

Rapidly growing small peripheral lung cancers detected by screening CT: correlation between radiological appearance and pathological features.

12 peripheral small lung cancers (< 20 mm) of rapid growth (volume doubling time < 150 days), detected by repeated low dose CT screening, were evaluated to examine their CT features and to correlate such features with histopathological findings. Each patient's CT images, including follow-up and thin section CT images, were studied retrospectively to determine tumour growth rate and CT morphological features. Nine of the tumours exhibited a solid tumour growth pattern: seven of these showed a well defined, homogeneous, soft tissue density with spicular or lobulated margin. These seven tumours included small cell lung cancer (n = 3), moderately differentiated adenocarcinoma (n = 2), poorly differentiated adenocarcinoma (n = 1) and squamous cell carcinoma (n = 1). The other two tumours, a moderately differentiated adenocarcinoma and a well differentiated adenocarcinoma, appeared as irregular, soft tissue density nodules with poorly defined margins. The latter exhibited an air bronchogram pattern and a small cavity. The remaining three tumours exhibited a lepidic tumour growth pattern. They showed ground glass opacity or ground glass opacity with a higher density central zone on CT images and were well differentiated adenocarcinomas. In conclusion, most peripheral small lung cancers of rapid growth were adenocarcinomas. They also included small cell lung cancer and squamous cell carcinoma. The majority showed solid tumour growth pattern and lacked an air bronchogram and/or small air spaces in the nodule. Some well differentiated adenocarcinomas with lepidic tumour growth pattern also showed rapid growth.

Adenocarcinoma↗

PubMed2000

Role of chemokines in inflammation and immunoregulation.

Chemokines are first noted for their ability to attract and activate leukocytes, as well as their potential role as mediators of inflammation. However, emerging data have shown that various chemokines may exert other biologic effects both inside and outside the immune system. Inducible chemokines participate primarily in inflammatory responses and comprise the bulk of the chemokine family. Constitutive chemokines are expressed primarily in secondary lymphoid organs and some nonlymphoid organs, where they play a major role in lymphocyte homing. Studies expanding to areas beyond inflammatory leukocyte recruitment will likely give us a more complete picture of chemokine function, its regulation in lymphoid and nonlymphoid tissues, and ways of utilizing endogenous chemokines to intervene with immune and inflammatory reactions.

Animals↗

PubMed2000

Role of p53 in cellular response to anticancer nucleoside analog-induced DNA damage.

Anticancer nucleoside analogs (e.g., ara-C, gemcitabine, fludarabine) induce apoptosis by incorporation into DNA. Removal of incorporated analogs from DNA by 3'-5' exonucleases is presumably a mechanism of drug resistance. Based on our previous observation that the 3'-5' exonuclease activity of wild-type (wt) p53 protein is able to preferentially remove mismatched nucleotides from DNA, in the present study we further investigated the ability of p53 to recognize and remove incorporated therapeutic analogs from DNA and its role in analog-induced apoptosis. We demonstrated that although the 3'-5' exonuclease of wt p53 protein was able to bind and excise the nucleoside analog residues from DNA in vitro, removal of the drug molecules from cellular DNA was slow in whole cells with wt p53 cells, and not detectable in mutant p53 cells. Furthermore, the wt p53 were more sensitive to the cytotoxic effect of the drugs compared to the p53-null or mutant cells. Incubation of ML-1 cells (wt p53) with gemcitabine caused an accumulation of p53 protein in their nuclei and preferentially induced apoptosis in the p53-positive cells, whereas the p53-negative cells remained intact. Transfection of p53-null cells with wt p53 expression vector enhanced the sensitivity of the cells to gemcitabine. Gel mobility shift assay using synthetic DNA containing gemcitabine as the probe suggests that p53 protein is likely to participate in the binding of the analog-containing DNA. Our study suggests that recognition of the incorporated nucleoside analogs in DNA by wt p53 did not confer resistance to the drugs, but it facilitated the apoptotic cell death process.

Antineoplastic Agents↗

PubMed2000

Expression of vascular endothelial growth factor and microvessel density in head and neck tumorigenesis.

Angiogenesis is a fundamental process in tumor growth and metastasis, and its significance and that of vascular endothelial growth factor (VEGF) expression as prognostic indicators have been documented for various types of human tumors. However, the mechanisms responsible for angiogenesis in head and neck squamous cell carcinoma are not well defined. To examine the relationship between angiogenesis and the phenotypic progressions of head and neck tumorigenesis, we used immunohistochemistry to analyze VEGF expression and microvessel density in 70 paraffin-embedded specimens that contained adjacent normal epithelium, premalignant lesions, or both from 57 patients with head and neck squamous cell carcinoma. Ten samples of normal oral mucosa were obtained from people who did not smoke or drink alcohol and included in the analysis as normal controls. Microvessel density was evaluated by averaging 10 microscopic fields (x400) in a defined area of each specimen. The degree of VEGF expression was assessed on a cell-by-cell basis in 10 microscopic fields (x200) in a defined area on a scale ranging from 0 (no expression) to 3+ (highest level of expression). In addition, the weighted mean index of VEGF expression was calculated. The mean +/- SD weighted mean index of VEGF expression in normal control epithelium (1.10 +/- 0.38, n = 10) was higher than it was in adjacent normal epithelium (0.82 +/- 0.27, n = 13; P = 0.04). VEGF expression decreased as samples ranged from normal adjacent epithelium to hyperplasia (0.78 +/- 0.28, n = 21), mild dysplasia (0.70 +/- 0.29, n = 28), moderate dysplasia (0.67 +/- 0.29, n = 11), severe dysplasia (0.51 +/- 0.39, n = 6), and squamous cell carcinoma (0.20 +/- 0.27, n = 70; overall P = 0.0001). VEGF expression was two times lower in cases with nodal disease (0.17 +/- 0.26, n = 29) than it was in nonnodal disease (0.32 +/- 0.29, n = 16; P = 0.02). Microvessel density showed no significant difference from adjacent normal epithelium premalignant lesions to cancer. In tumor, no correlation was seen between VEGF expression or microvessel density and differentiation, primary tumor site, T stage, or smoking status. These findings indicate that VEGF expression is down-regulated during head and neck tumorigenesis. However, further studies are required to better understand the mechanism of VEGF down-regulation in head and neck tumorigenesis.

Adult↗

PubMed2000

Risk of colorectal cancer in patients with hematologic disease.

BACKGROUND AND AIMS: A relatively large number of patients with multiple myeloma have been reported to develop a secondary malignancy such as cancer of the breast, biliary system or bowel. METHODS: A retrospective study was perfomed in 734 patients with hematologic disease diagnosed at Nippon Medical School Hospital between May 1984 and September 1994 to determine the incidence of colorectal cancer in these patients based on a history review, colonoscopic findings, and surgical or autopsy data. RESULTS: Of the 734 patients, 14 (1.9%) had colorectal cancer; two of 11 patients (18.2%) had pure red cell aplasia; two of 25 patients (8%) had multiple myeloma; and three of 46 patients (6.5%) had aplastic anemia. Patients with pure red cell aplasia, multiple myeloma or aplastic anemia had colorectal cancer at a significantly higher rate compared to those with leukemia (P< 0.005, P< 0.02, P< 0.01, respectively). CONCLUSIONS: It is possible that a relatively large number of patients with pure red cell aplasia, multiple myeloma or aplastic anemia will develop a colorectal cancer.

Aged↗

PubMed2000

[Study on hepatitis B virus infection status in placentas of hepatitis B surface antigen positive pregnant women during middle and late period of pregnancy].

OBJECTIVE: To investigate Hepatitis B Virus (HBV) infection status in placentas of Hepatitis B Surface Antigen (HBsAg) positive pregnant women during middle and late period of pregnancy. METHODS: One hundred and sixty-seven placentas from HBsAg positive pregnant women were collected, including 158 term placentas and 9 aborted second-trimester placentas. HBsAg and hepatitis B core antibody (HBcAg) in placental cytotypes were detected by immunohistochemistry. RESULTS: Of the 158 term placentas, HBV infection rates in decidual cells (DC), trophoblastic cells (TC), villous mesenchymal cells (VMC) and villous capillary endothelial cells (VCEC) were 66.46% (105/158), 58.23% (92/158), 27.22% (43/158) and 12.66% (20/158), respectively. The HBV infection rates gradually decreased from maternal side to fetal side of placentas. Both HBsAg and HBcAg were mainly located in the cytoplasm of infected cells. The positive cells were mostly in focal distribution. One out of 9 aborted second-trimester placentas was infected. CONCLUSIONS: HBV infection was found in different cells of term placentas. The positive rates for HBsAg and HBcAg in placentas were gradually decreased from maternal side to fetal side. The positive rate was low in aborted second-trimester placentas.

Adult↗

PubMed2000

Asymmetry of brain functional activation: fMRI study under language and music stimulation.

OBJECTIVE: To determine the asymmetry of the human brain functional activation. METHODS: With the help of GE Signa Horizon MRI system, 14 cases of right-handed volunteers were examined and the blood oxygenation level dependent method was used. The T1-weighted images were obtained with spin echo pulse sequence and the functional imaging (T2*-weighted) was performed using a single shot echo planar imaging pulse sequence. Data analysis was done with Sun Sparc Workstation and by the method of student t test or correlation analysis. RESULTS: Most of activation areas were in the left hemisphere under language stimulation, while they were in the right side under music stimulation. Besides, a few brain areas in the contralateral cerebral cortex were also activated under both stimulations. CONCLUSION: The present study supported the hypothesis of the asymmetry of brain functional activation and many brain areas of the cerebral cortex as well as both hemispheres worked in coordination. In addition, it also proved that fMRI is a feasible method in the study of human brain in vivo.

Acoustic Stimulation↗

PubMed2000

[The dynamics of pH, free calcium and total proteins in root plaque fluid and their relationships to the cariogenic potential].

OBJECTIVE: To enhance knowledge of root caries by analysis of the dynamics of dental plaque fluids on root surface and their relationships with the caries history. METHODS: The pH, free calcium and total proteins of dental plaque fluids on sound root surfaces were analyzed before and after the sucrose challenge. Subjects were either root caries-free (RCF) or caries-positive (RCP). RESULTS: After a sucrose challenge, the pH of plaque fluids dropped significantly and the concentration of free calcium increased significantly. There were no statistical differences in pH (RCF group 6.24 +/- 0.74, RCP group 5.96 +/- 0.70) and free calcium [RCF group (0.60 +/- 0.46) mmol/L, RCP group (0.89 +/- 0.54) mmol/L] between RCF and RCP group before sucrose challenge. Following sucrose exposure, pH (5.14 +/- 0.19) and free calcium [(1.73 +/- 0.74) mmol/L] in RCP group were significantly lower than RCP group [(pH 5.28 +/- 0.16), free calcium (2.73 +/- 1.25) mmol/L]. No interrelationship has been found between the amount of total proteins and free calcium. Components (contents, change trend) in root plaque were strongly related to that in coronal plaque. CONCLUSIONS: The process of root caries may be consistent to coronal caries regarding to the acid production of bacteria after a sucrose challenge. Plaque compositions show a stronger cariogenic potential in RCP group.

Calcium↗

PubMed1999

Structure of 1-aminocyclopropane-1-carboxylate synthase, a key enzyme in the biosynthesis of the plant hormone ethylene.

The 2.4 A crystal structure of the vitamin B6-dependent enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase is described. This enzyme catalyses the committed step in the biosynthesis of ethylene, a plant hormone that is responsible for the initiation of fruit ripening and for regulating many other developmental processes. ACC synthase has 15 % sequence identity with the well-studied aspartate aminotransferase, and a completely different catalytic activity yet the overall folds and the active sites are very similar. The new structure together with available biochemical data enables a comparative mechanistic analysis that largely explains the catalytic roles of the conserved and non-conserved active site residues. An external aldimine reaction intermediate (external aldimine with ACC, i.e. with the product) has been modeled. The new structure provides a basis for the rational design of inhibitors with broad agricultural applications.

Amino Acid Sequence↗