Evidence that an additional mutation is required to tolerate insertional inactivation of the Streptomyces lividans recA gene

In contrast to recA of other bacteria, the recA gene of Streptomyces lividans has been described as indispensable for viability (G. Muth, D. Frese, A. Kleber, and W. Wohlleben, Mol. Gen. Genet. 255:420-428, 1997.). Therefore, a closer analysis of this gene was performed to detect possible unique features distinguishing the Streptomyces RecA protein from the well-characterized Escherichia coli RecA protein. The S. lividans recA gene restored UV resistance and recombination activity of an E. coli recA mutant. Also, transcriptional regulation was similar to that of E. coli recA. Gel retardation experiments showed that S. lividans recA is also under control of the Streptomyces SOS repressor LexA. The S. lividans recA gene could be replaced only by simultaneously expressing a plasmid encoded recA copy. Surprisingly, the recA expression plasmid could subsequently be eliminated using an incompatible plasmid without the loss of viability. Besides being UV sensitive and recombination deficient, all the mutants were blocked in sporulation. Genetic complementation restored UV resistance and recombination activity but did not affect the sporulation defect. This indicated that all the recA mutants had suffered from an additional mutation, which might allow toleration of a recA deficiency.

Effects of thoracic epidural anesthesia with and without autonomic nervous system blockade on cardiac monophasic action potentials and effective refractoriness in awake dogs

BACKGROUND

The effects of thoracic epidural anesthesia (TEA) on myocardial repolarization and arrhythmogenicity are only incompletely understood. This is primarily because of the lack of appropriate experimental models. In most of the studies performed thus far, TEA was used in anesthetized animals. Baseline anesthesia itself may have modified the effects of TEA. This study investigates right atrial and ventricular repolarization by recording monophasic action potentials after TEA in awake dogs. The authors hypothesized that an antiarrhythmic role of TEA exists, which may be related to a direct effect of TEA on myocardial repolarization.

METHODS

The hypothesis was tested in an in vivo canine model, in which atrial and ventricular myocardial action potential duration and refractoriness are recorded by means of monophasic action potential catheters.

RESULTS

Thoracic epidural anesthesia significantly increased ventricular monophasic action potential duration for cycle lengths shorter than 350 ms. Changes in monophasic action potential duration were paralleled by a concomitant prolongation of effective refractory period (ERP) at higher rates so that the ratio of ERP to action potential duration was unaffected.

CONCLUSIONS

This model helps to study the role of TEA on ventricular repolarization and arrhythmogenicity. Because lengthening of repolarization and prolongation of refractoriness may, in some circumstances, be antiarrhythmic, TEA may be protective against generation of ventricular arrhythmias mediated, e.g., by increased sympathetic tone. The results also imply that the beneficial role of TEA might be stronger at the ventricular site as compared with the atrium. At atrial sites there was only a trend toward prolongation of repolarization even at short cycle lengths.

Antibiotic-seeking behavior in college students: what do they really expect?

Injudicious use of antibiotics contributes to increased bacterial resistance, and patient expectations encourage physicians to overuse antibiotics. The authors evaluated the level of ill college students' antibiotic-seeking behavior to determine if receiving an antibiotic prescription influenced patients' satisfaction with visits to a clinician. Of 129 students with upper respiratory complaints presenting to a university health center, 55% expected an antibiotic prescription. Antibiotic expectation was significantly more likely among students who thought they had a bacterial versus a viral infection (90% vs 40%; p < .01). A clear diagnosis, an explanation of the rationale for treatment, and an antibiotic prescription were significantly associated with patient satisfaction. Clinicians prescribed an antibiotic for 36% of the students; only 13% of these 46 had requested an antibiotic during the visit. At some previous time, one third of the students had taken an antibiotic prescribed for an earlier illness or for another person. Better patient education and improved clinician-patient communication can potentially help to reduce the injudicious use of antibiotics.

Surgical treatment of parathyroid carcinoma (Review)

Cancer of the parathyroid gland is rare and most patients suffer from hyperparathyroidism (HPT). Therefore it is often difficult to distinguish between benign HPT and malignant disorders. Prognosis as well as therapeutic approaches are still limited. Surgical treatment should be considered the therapy of choice for primary and recurrent manifestation of parathyroid carcinoma. The initial operation includes en-bloc resection of the tumor and the ipsilateral thyroid lobe. Surgery may cure some patients, but is often only palliative and aims to control hypercalcemia. In some patients hypercalcemia may be refractory to repeated surgery and medical treatment can provide short- or middle-term effects.

Effects of transdermal testosterone gel on bone turnover markers and bone mineral density in hypogonadal men

OBJECTIVE

Androgen replacement has been reported to increase bone mineral density (BMD) in hypogonadal men. We studied the effects of 6 months of treatment with a new transdermal testosterone (T) gel preparation on bone turnover markers and BMD.

DESIGN

This was a prospective, randomized, multicentre, parallel clinical trial where 227 hypogonadal men, mean age 51 years (range: 19-68 years) were studied in 16 academic and research institutions in the USA. Subjects were randomized to apply 1% T gel containing 50 or 100 mg T (delivering approximately 5-10 mg T/day) or two T patches (delivering 5 mg T/day) transdermally for 90 days. At day 91, depending on the serum T concentration, the T gel dose was adjusted upward or downward to 75 mg T/day until day 180. No dose adjustment occurred in the T patch group.

MEASUREMENTS

Serum T, free T and oestradiol, bone turnover markers and BMD were measured on days 0, 30, 90 and 180 before and after treatment.

RESULTS

Application of T gel 100 mg/day resulted in serum T concentrations 1.4 and 1.9-fold higher than in the T gel 50 mg/day and the T patch groups, respectively. Proportional increases occurred in serum oestradiol. Urine N-telopeptide/creatinine ratio, a marker for bone resorption, decreased significantly (P = 0.0019) only in the T gel 100 mg/day group. Serum bone osteoblastic activity markers (osteocalcin, procollagen and skeletal alkaline phosphatase) increased significantly during the first 90 days of treatment without intergroup differences but declined to baseline thereafter. BMD increased significantly both in the hip (+1.1 +/- 0.3%) and spine (+2.2 +/- 0.5%) only in the T gel 100 mg/day group (P = 0.0001).

CONCLUSIONS

Transdermal testosterone gel application for 6 months decreased bone resorption markers and increased osteoblastic activity markers for a short period, which resulted in a small but significant increase in BMD. Ongoing long-term studies should answer whether the observed increases in BMD are sustained or continue to be dependent on the dose of testosterone administered.

Minimal residual disease in thyroid carcinoma

The detection of disseminated tumor cells in differentiated (DTC) and medullary thyroid carcinomas (MTC) is one of the main topics in current thyroid cancer research. Immunocytochemistry and polymerase chain reaction (PCR) provide the tools for the identification of a small number of thyroid cancer cells in peripheral blood and cervical lymph nodes. Thyroid-specific markers, such as thyroglobulin (Tg) mRNA and thyroid peroxidase (TPO) mRNA, have been detected with RT-PCR in blood samples of tumor patients and healthy control subjects. To prevent false-positive results, quantitative PCR systems were established. Tumor-specific markers, such as telomerase activity and cytokeratin 20 (CK20), have been detected in various epithelial tumors. Amplification products of these markers were found in blood samples and in fine-needle aspiration (FNA) biopsies of patients with thyroid carcinomas. Using molecular detection of disseminated tumor cells in cervical lymph nodes with CK20 RT-PCR, a higher percentage of involved lymph nodes was detected compared to immunohistochemistry. The results of the presented studies may help researchers to develop more sensitive methods for early tumor cell dissemination, and refine risk groups that might benefit from more extensive surgical procedures or adjuvant therapy. However, the prognostic value of minimal residual disease (MRD) in thyroid carcinoma has to be confirmed in large or multicenter prospective studies.

[Acute coronary syndromes: an update. I. Pathogenesis and drug therapy]

BACKGROUND

Unstable angina accounts for more than one million hospital admissions annually. 6-8% of patients with this condition have non-fatal myocardial infarction or die within the first year after diagnosis. Recently, the term "acute coronary syndromes" has been used to describe the spectrum of conditions that includes unstable angina, non-Q-wave myocardial infarction (which generally presents without ST-segment elevation), and Q-wave myocardial infarction (which generally presents with ST-segment elevation).

PATHOGENESIS

Disruption of a formed plaque is a complex pathologic process that is central to the initiation of the acute coronary syndromes. Local thrombosis occurring after plaque disruption results from complex interactions among the lipid core, smooth-muscle cells, macrophages, and collagen.

TREATMENT

Multiple huge clinical trials confirmed that aspirin reduces the risk of death from cardiac causes and fatal and non-fatal myocardial infarction by about 50-70% in patients presenting with unstable angina. Ticlopidine may be substituted for aspirin in patients with hypersensitivity to aspirin or gastrointestinal intolerance. Clopidogrel acts similarly to ticlopidin but has fewer side effects than ticlopidine and has not been reported to cause neutropenia. High-risk patients with refractory unstable angina and elevated troponin levels may have substantial benefit of glycoptotein (GP) IIb/IIIa inhibition. Current practice guidelines support the use of the combination of unfractionated heparin and aspirin for the treatment of unstable angina. Clinical studies have demonstrated that the incidence of the composite end point of death, myocardial infarction, or recurrent angina was lower with enoxaparin than with unfractionated heparin. Beta-blockers, nitrates, and calcium-channel blockers are useful for antiischemic therapy in patients with acute coronary syndromes.

[Acute coronary syndromes: an update. II. Coronary revascularization and risk stratification]

CORONARY REVASCULARIZATION: PTCA in patients with refractory unstable angina is associated with a substantial risk of the following complications: death, myocardial infarction, need for emergency surgery, and restenosis. The introduction of intracoronary stents, however, has improved both short-term and long-term outcomes. The newer adjunctive pharmacologic therapies enhance even further the benefits associated with the use of stents. The decision regarding the specific revascularization procedure to be used (e.g., CABG, PTCA, stent placement, or atherectomy) is based on the coronary anatomy, the left ventricular function, the experience of the medical and surgical personnel, the presence or absence of coexisting illnesses, and the preferences of both the patient and the physician.

RISK STRATIFICATION

Among patients with unstable angina or non-Q-wave myocardial infarction, there is an increased risk of death within 6 weeks in those with elevated troponin I levels and the risk of death continues to increase as the troponin level increases. Reversible ST segment depression is associated with an increase by a factor of 3-6 in the likelihood of death, myocardial infarction, ischemia at rest, or provocable ischemia during a test to stratify risk. Exercise or pharmacologic stress testing provides important information about a patient's risk. Although the conditions of the majority of patients with unstable angina will stabilize with effective antiischemic medications, approximately 50-60% of such patients will require coronary angiography and revascularization because of the "failure" of medical therapy. High-risk patients are those who have had angina at rest, prolonged angina, or persistent angina with dynamic ST segment changes or hemodynamic instability, and they urgently require simultaneous invasive evaluation and treatment. Medical therapy should be adjusted rapidly to relieve manifestations of ischemia and should include antiplatelet therapy (aspirin, or ticlopidine or clopidogrel if aspirin is contraindicated), antithrombotic therapy (unfractionated heparin or low-molecular-weight heparin), beta-blockers, nitrates, and possibly calcium-channel blockers. Early administration of glycoprotein IIb/IIIa inhibitors may be particularly important, especially in high-risk patients with positive troponin tests or those in whom implantation of coronary stents is anticipated.

Cellular and humoral immune response in progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a fatal, demyelinating disease caused by JC virus (JCV) in patients with severe immunosuppression. We studied the JCV-specific cellular and humoral immune response in 7 healthy donors (HD), 6 human immunodeficiency virus-1 (HIV-1)-infected patients without PML (HIV), 4 HIV-1-negative patients with PML (PML), and 8 HIV-1-positive patients with PML (HIV/PML). As antigens, recombinant virus-like particles of the major structural protein VP1 (VP1-VLP) of JCV, tetanus toxoid (TT), or the mitogen phytohemagglutinin (PHA) were used. Proliferation of peripheral blood mononuclear cells (PBMC) after stimulation with the VP1-VLP was significantly suppressed in PML and HIV/PML patients compared to HD. After antigen stimulation the production of interferon-gamma (IFN-gamma) was reduced in PML, in HIV/PML, and in HIV patients. The production of interleukin-10 (IL-10), however, was elevated in HIV/PML patients. Neither proliferation nor cytokine production correlated with the presence of JCV DNA in PBMC. The immunoglobulin G serum antibody titer to the VP1-VLP was slightly elevated in HIV, elevated in PML, and highly elevated in HIV/PML patients compared to HD. The development of PML appears to coincide with a general impairment of the Th1-type T-helper cell function of cell-mediated immunity.

[Hepatitis B screening of pregnant women and follow-up vaccination of infants with HBsAG positive mothers. A survey from the Hvidovre hospital in 1999]

The aim of this study was to assess the implementation of the recommendations of the Danish National Health Service concerning screening of women from hepatitis B (HB) endemic areas and follow-up vaccination of infants of carrier mothers. We examined all birth notification (n = 836) at Hvidovre Hospital during the first three months of 1999. Among 188 women from HB endemic areas only 134 (71%) women had been screened for HBsAg before delivery. Six women were HBsAg positive one of whom was examined after the delivery. Four out of six infants (67%) received Aunativ and Engerix-B within 12 hours of birth, one infant received Aunativ and Engerix-B at four days of age, the infant born of the mother who was screened after delivery didn't receive either Aunativ or Engerix-B. Three out of the six infants (50%) had received all the scheduled Engerix-B vaccinations. Our results suggest it may be necessary to reconsider the current screening and vaccination procedures to prevent an increase in the number of children becoming chronic HB carriers in Denmark.

[Coronary artery bypass graft dysfunction--clinical presentation, laboratory and electrocardiographic parameters]

The recurrence of symptoms after coronary artery bypass surgery is often caused by bypass-dysfunction. In this study we tried to determine factors related to the long-term patency of arterial and venous bypass grafts. We evaluated all patients with bypass grafts undergoing coronary angiography in the year 1998 at our hospital (163 patients, mean age 67 years, mean interval since the operation 79 months, a total of 341 venous bypasses (VBP), 386 peripheral venous anastomoses and 85 arterial (LIMA = left internal mammarial artery) bypasses. The data were collected by a retrospective analysis of the hospital records. Statistics were performed using the Wilcoxon-Mann-Whitney-U test. After an interval of 53 months LIMA-bypasses were patent without stenosis in 92%. Symptoms were caused in only 2% by a dysfunction of the LIMA-graft. The patency of venous bypass grafts decreased with time (5 years after the operation 74% were patent without stenosis, 5-10 years 56%, more than 10 years 35%, p < 0.01). We found clear relations between the function of the venous grafts and the clinical presentation (patent grafts without stenosis in 43% with acute coronary syndromes, in 57% with stable angina [p = 0.08] and in 86% with atypical angina [p < 0.0001 for the difference between each of the first two and the last syndrome]), the resting-ECG (65% patent VBP without stenosis with normal ST-segments and 49% with abnormal ST-segments, p < 0.01), the body-mass-index (70% patent VBP without stenosis with a BMI < 25 and 56% with a BMI > 30, p = 0.05) and the erythrocyte sedimentation rate after 2 hours (79% patent VBP with an ESR < or = 20 mm vs. 64% with an ESR > 49 mm, p = 0.02). The function of VBP after coronary artery bypass graft (CABG)-procedure depends primarily upon the interval since the operation. In addition, we found correlations with clinical presentation, resting-ECG, body-mass-index and erythrocyte-sedimentation rate as a possible marker of inflammation in bypass-atherosclerosis. Therefore, inflammatory processes seem to play an important role in the development of venous graft dysfunction.

[Pharmacologic interventions in primary prevention: lipid lowering drugs, aspirin, antiobesity drugs, and antihypertensive agents]

Heart disease, particularly coronary heart disease is a major cause of morbidity and mortality in developed countries. Cardiovascular disease accounts for more than 50% of deaths. Drug therapy is highly effective for treatment of patients after a first cardiovascular event (secondary prevention). In contrast, introduction of drug therapy for lowering cardiovascular risk before a first cardiovascular event (primary prevention) is discussed controversially. The number of persons who need to be treated for prevention of one cardiovascular event is high and drug therapy in more or less "healthy" people is justified only after accurate assessment of potential risks and possible beneficial effects. Drug therapy combined with non-pharmacological treatment strategies is considered to be appropriate in selected high-risk persons for primary prevention. The following article describes potential indications of several drugs, in particular cholesterol-lowering therapy, aspirin, drug therapy of obesity and hypertension, for use in primary prevention of cardiovascular disease.

Inhibition of inflammatory endothelial responses by a pathway involving caspase activation and p65 cleavage

Suppression of NF kappa B activation has been involved in the elimination of survival programs during endothelial cell (EC) apoptosis. We used alpha-tocopheryl succinate (alpha-TOS) to trigger apoptosome formation and the subsequent activation of executioner caspases. The level of bcl-2 was reduced by alpha-TOS, and its downregulation potentiated and its overexpression suppressed pro-apoptotic effects of alpha-TOS, indicating a mitochondrial role in alpha-TOS-induced apoptosis in EC. alpha-TOS treatment was associated with induction of TUNEL-positive apoptosis in EC with a high but not with a low proliferation index. The use of the pan-caspase inhibitor z-VAD.fmk suggested the involvement of caspases in cleavage of p65, and in inhibition of nuclear translocation of p65 and NF kappa B-dependent transactivation of a gene construct encoding the green fluorescence protein elicited by TNF alpha in contact-arrested EC. The suppression by alpha-TOS of inflammatory EC responses induced by TNF alpha such as VCAM-1 mRNA and surface protein expression and shear-resistant arrest of monocytic cells were also reversed by z-VAD.fmk. NF kappa B-dependent transactivation was preserved in alpha-TOS-treated EC stably transfected with a caspase-noncleavable p65 mutant but not with its truncated form, thus establishing a direct link between alpha-TOS-induced effects and p65 cleavage. Our data infer a pathway by which caspase activation in EC inhibits NF kappa B-dependent inflammatory activation and monocyte recruitment, and provide evidence for a relationship between pro-apoptotic and anti-inflammatory pathways.

[Homocysteine and cardiovascular risk]

Homocysteine is an amino acid that plays a key role in methionine- and homocysteine metabolism. Homocystinuria has been described about four decades ago to be an inherited (autosomal recessive) disorder with rapid progressive atherosclerosis. Thus, homocysteine has been investigated intensively with respect to vascular wall injury and atherogenesis. Folic acid and vitamin B12 are cofactors of methioninsynthase, a key enzyme in homocysteine metabolism. Plasma levels of homocysteine are higher in patients with coronary artery disease documented by coronary angiography than in individuals with normal coronary arteries. Supplementation of folic acid is the treatment of choice to lower plasma homocysteine concentrations. Improvement in endothelial function could be documented in patients with folic acid supplementation. Large scaled clinical trials investigating folic acid supplementation in secondary prevention are now in progress. Today, homocysteine and its association with atherosclerosis raise a lot of questions to be answered. A distinct pathophysiological model linking hyperhomocysteinaemia and atherosclerosis is still not available. The presence of hyperhomocysteinemia in atherosclerotic vascular disease as a surrogate with no pathophysiological relevance itself cannot be ruled out. Routine testing of homocysteine levels is not yet recommended. Treatment of patients with folic acid or vitamin B for primary and secondary prevention of atherosclerotic vascular disease cannot be recommended today, because large scaled intervention trials on homocysteine lowering by vitamin B or folic acid are not available yet. Possible effects of these interventions on acute vascular events are not known.

In vivo recording of monophasic action potentials in awake dogs--new applications for experimental electrophysiology

INTRODUCTION

Despite enormous developments in the field of clinical and experimental electrophysiology there is still a gap in evaluating repolarization in the awake animal. Numerous previous studies have used monophasic action potentials (MAP) to assess repolarization in vitro and in vivo in anesthetized animal models. However, an approach for recording MAP in awake dogs without interference of anesthesia has not yet been developed.

METHODS AND RESULTS

We developed an experimental technique to record MAP in conscious dogs by means of conventional rubber introducers which were implanted into the internal jugular vein. In seven awake dogs, atrial as well as ventricular MAP were simultaneously measured without complications. Pacing thresholds were low and stable over time ranging from 0.2 to 4.0 mA. The MAP amplitudes ranged from 10 to 30 mV for ventricular and from 5 to 15 mV for atrial MAP. Continuous MAP recordings of stable amplitude could be made from the same endocardial site for periods of up to one hour. Antegrade and retrograde AV-nodal conduction properties could be assessed. Programmed stimulation was performed to simultaneously determine local refractory periods and MAP duration at cycle lengths from 500 to 200 ms.

CONCLUSION

In awake, unsedated dogs the measurement of MAP via rubber introducers permits safe, long-term recording of MAP. Such recordings may be useful for safety pharmacological studies in evaluating cardiovascular and non-cardiovascular drugs with regard to their effects on repolarization. In various canine in vivo models including in vivo models of long QT syndrome, heart failure or sudden cardiac death, the present technique permits electrophysiological measurements without interference of anesthesia.

Atomic dynamics in single and multi-photon double ionization: An experimental comparison

We have used a multi-particle imaging technique (COLTRIMS) to observe the double ionization of rare gas atoms by multi-photon absorption of 800 nm (1.5 eV) femto-second laser pulses and by single photon absorption (synchrotron radiation). Both processes are mediated by electron correlation. We discuss similarities and differences in the three-body final state momentum distributions.

Measurement of CP-violating asymmetries in B0 decays to CP eigenstates

We present measurements of time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurement uses a data sample of 23x10(6) Upsilon(4S)-->BbarB decays collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we find events in which one neutral B meson is fully reconstructed in a CP eigenstate containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay time distributions in such events. The result is sin2beta = 0.34+/-0.20 (stat)+/-0.05 (syst).

Strong correlations in the He ground state momentum wave function observed in the fully differential momentum distributions for the p + He transfer ionization process

The four-particle process of proton-helium transfer ionization has been studied using cold target recoil ion momentum spectroscopy to measure the momenta of all three particles in the final state. Most of the electrons are emitted in the H0 scattering plane and in the backward direction. The final state momentum distributions show discrete structures very different from those expected for uncorrelated capture and ionization. The measured momentum pattern is interpreted to be due to a new transfer ionization reaction channel which results from strong correlations in the initial He ground state momentum wave function.

Ceramide as an activator lipid of cathepsin D

We have identified the aspartic protease cathepsin D as a novel intracellular target protein for the lipid second messenger ceramide. Ceramide specifically binds to and induces CTSD proteolytic activity. A-SMase deficient cells derived from Niemann-Pick patients show decreased CTSD activity that was reconstituted by transfection with A-SMase cDNA. Ceramide accumulation in cells derived from A-ceramidase defective Farber patients correlates with enhanced CTSD activity. These findings suggest that A-SMase-derived ceramide targets endolysosomal CTSD.

Identification of synapsin I peptides that insert into lipid membranes

The synapsins constitute a family of synaptic vesicle-associated phosphoproteins essential for regulating neurotransmitter release and synaptogenesis. The molecular mechanisms underlying the selective targeting of synapsin I to synaptic vesicles are thought to involve specific protein-protein interactions, while the high-affinity binding to the synaptic vesicle membrane may involve both protein-protein and protein-lipid interactions. The highly hydrophobic N-terminal region of the protein has been shown to bind with high affinity to the acidic phospholipids phosphatidylserine and phosphatidylinositol and to penetrate the hydrophobic core of the lipid bilayer. To precisely identify the domains of synapsin I which mediate the interaction with lipids, synapsin I was bound to liposomes containing the membrane-directed carbene-generating reagent 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine and subjected to photolysis. Isolation and N-terminal amino acid sequencing of 125I-labelled synapsin I peptides derived from CNBr cleavage indicated that three distinct regions in the highly conserved domain C of synapsin I insert into the hydrophobic core of the phospholipid bilayer. The boundaries of the regions encompass residues 166-192, 233-258 and 278-327 of bovine synapsin I. These regions are surface-exposed in the crystal structure of domain C of bovine synapsin I and are evolutionarily conserved among isoforms across species. The present data offer a molecular explanation for the high-affinity binding of synapsin I to phospholipid bilayers and synaptic vesicles.

Induction of cancer cell apoptosis by alpha-tocopheryl succinate: molecular pathways and structural requirements

The vitamin E analog alpha-tocopheryl succinate (alpha-TOS) can induce apoptosis. We show that the proapoptotic activity of alpha-TOS in hematopoietic and cancer cell lines involves inhibition of protein kinase C (PKC), since phorbol myristyl acetate prevented alpha-TOS-triggered apoptosis. More selective effectors indicated that alpha-TOS reduced PKCalpha isotype activity by increasing protein phosphatase 2A (PP2A) activity. The role of PKCalpha inhibition in alpha-TOS-induced apoptosis was confirmed using antisense oligonucleotides or PKCalpha overexpression. Gain- or loss-of-function bcl-2 mutants implied modulation of bcl-2 activity by PKC/PP2A as a mitochondrial target of alpha-TOS-induced proapoptotic signals. Structural analogs revealed that alpha-tocopheryl and succinyl moieties are both required for maximizing these effects. In mice with colon cancer xenografts, alpha-TOS suppressed tumor growth by 80%. This epitomizes cancer cell killing by a pharmacologically relevant compound without known side effects.

Exploring the domain structure of modular nonribosomal peptide synthetases

Recently, considerable insight has been gained into the modular organization of nonribosomal peptide synthetases (NRPS). The three-dimensional structures of domains associated with substrate adenylation and covalent binding have been solved as well as the structure of a priming enzyme required for the post-translational modification of NRPS. Taken together, these studies will help us to understand the architecture of these mega-enzymes.