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K Nordstrand

Publications and source records attributed to K Nordstrand.

At least 19 recordsLinked to original sources
PubMed2001

Structure, dynamics and electrostatics of the active site of glutaredoxin 3 from Escherichia coli: comparison with functionally related proteins.

The chemistry of active-site cysteine residues is central to the activity of thiol-disulfide oxidoreductases of the thioredoxin superfamily. In these reactions, a nucleophilic thiolate is required, but the associated pK(a) values differ vastly in the superfamily, from less than 4 in DsbA to greater than 7 in Trx. The factors that stabilize this thiolate are, however, not clearly established. The glutaredoxins (Grxs), which are members of this superfamily, contain a Cys-Pro-Tyr-Cys motif in their active site. In reduced Grxs, the pK(a) of the N-terminal active-site nucleophilic cysteine residue is lowered significantly, and the stabilization of the corresponding thiolate is expected to influence the redox potential of these enzymes. Here, we use a combination of long molecular dynamics (MD) simulations, pK(a) calculations, and experimental investigations to derive the structure and dynamics of the reduced active site from Escherichia coli Grx3, and investigate the factors that stabilize the thiolate. Several different MD simulations converged toward a consensus conformation for the active-site cysteine residues (Cys11 and Cys14), after a number of local conformational changes. Key features of the model were tested experimentally by measurement of NMR scalar coupling constants, and determination of pK(a) values of selected residues. The pK(a) values of the Grx3 active-site residues were calculated during the MD simulations, and support the underlying structural model. The structure of Grx3, in combination with the pK(a) calculations, indicate that the pK(a) of the N-terminal active-site cysteine residue in Grx3 is intermediate between that of its counterpart in DsbA and Trx. The pK(a) values in best agreement with experiment are obtained with a low (<4) protein dielectric constant. The calculated pK(a) values fluctuate significantly in response to protein dynamics, which underscores the importance of the details of the underlying structures when calculating pK(a) values. The thiolate of Cys11 is stabilized primarily by direct hydrogen bonding with the amide protons of Tyr13 and Cys14 and the thiol proton of Cys14, rather than by long-range interactions from charged groups or from a helix macrodipole. From the comparison of reduced Grx3 with other members of the thioredoxin superfamily, a unifying theme for the structural basis of thiol pK(a) differences in this superfamily begins to emerge.

Bacterial Proteins↗
PubMed2001

Myocardial performance after transmyocardial revascularization with CO(2)laser. A dobutamine stress echocardiographic study.

AIMS: Transmyocardial laser revascularization is a treatment for patients with severe angina pectoris not eligible for conventional revascularization. The effects on myocardial function and reversible ischaemia have not been clarified. METHODS AND RESULTS: One hundred patients with refractory angina not eligible for conventional revascularization were randomized 1:1 to receive continued optimal medical treatment or transmyocardial revascularization with CO(2)laser in addition to medical treatment. Dobutamine stress echocardiography examinations were performed at baseline and at 3 and 12 months after randomization. The effects of transmyocardial revascularization on myocardial function and reversible ischaemia were assessed by visual interpretation of cineloops at rest and during stress in a 16-segment model. After transmyocardial revascularization resting left ventricular wall motion abnormalities increased (P<0.01), whereas wall motion during dobutamine stimulation remained unchanged. The number of probably non-viable segments increased (P<0.01) with a corresponding decrease in the number of ischaemic segments. Fewer patients had the dobutamine infusion discontinued because of chest pain after transmyocardial revascularization with laser, but the chest pain threshold did not increase significantly. CONCLUSION: Following transmyocardial revascularization, resting wall motion abnormalities worsened, wall motion abnormalities during dobutamine stimulation remained unchanged and the number of probably non-viable segments increased.

Angina Pectoris↗
PubMed2001

Effects of transmyocardial revascularization on myocardial perfusion and systolic function assessed by nuclear and magnetic resonance imaging methods.

OBJECTIVE: There is no obvious explanation, except placebo, to the symptomatic effect of transmyocardial laser revascularization (TMR) in patients with refractory angina. Whether TMR improves myocardial perfusion or relieves symptoms without altering cardiac function is not clarified. METHODS: One hundred patients with refractory angina were randomized 1:1 to TMR (CO2 laser) and medical treatment, or medical treatment alone. Technetium 99m (99mTc)-tetrofosmin myocardial perfusion tomography (SPECT), quantitative myocardial perfusion gated SPECT (QGSPECT), technetium 99m (99mTc) multiple gated acquisition radionuclide ventriculografi (MUGA) and cine-magnetic resonance imaging (cine-MRI) were performed at baseline and after 3 and 12 months. RESULTS: Following TMR, a slight reduction in left ventricular ejection fraction (LVEF) (p < 0.05) was observed (MUGA and QGSPECT) compared to baseline. Inclusion of incomplete studies (QGSPECT) revealed a significant reduction in LVEF and increase in left ventricular end-diastolic volume (LVEDV) (p < 0.05) compared to a control group. Otherwise, no between-group comparisons showed statistically significant differences. CONCLUSION: TMR did not improve myocardial perfusion, but led to a reduction in LVEF and increase in LVEDV, however not significantly different from the control group.

Aged↗
PubMed2001

Cardiac enzymes after transmyocardial laser treatment with CO2 laser.

OBJECTIVES: The aim of the present study was to examine postoperative serum levels of cardiac enzymes after transmyocardial laser treatment (TML) and to evaluate any associations between this release, postoperative cardiac events and change in ejection fraction after 3 months' follow-up. DESIGN: Forty-nine patients with angina pectoris Canadian Cardiovascular Society Angina Score Class III & IV refractory to medical therapy and untreatable by coronary artery bypass or percutaneous transluminal angioplasty treated with CO2 laser were included. Inclusion criteria were age less than 75 years, left ventricular ejection fraction greater than or equal to 30% and myocardial regions with reversible ischemia. Serum levels of aspartate aminotranspherase (ASAT), alanine aminotranspherase (ALAT) and MB-isoenzymes of creatine kinase (CK-MB) were followed during the first 72 h after surgery. Ejection fractions were estimated by multiple-gated acquisition ventriculography at inclusion and 3 months postoperatively. RESULTS: A significant increase in serum markers of myocardial necrosis was observed 8 h after surgery. A subsequent increase from 8 to 24 h after surgery was associated with the presence of postoperative cardiac adverse events. An inverse correlation was found between peak level of cardiac enzymes and change in ejection fraction from baseline to 3 months' follow-up. CONCLUSIONS: TML with CO2 laser is followed by a significant increase in serum levels of cardiac enzymes after 8 h. Further significant increases are associated with cardiac adverse events postoperatively. Peak enzyme values are inversely correlated with change in ejection fraction from baseline to 3 months' follow-up.

Angina Pectoris↗
PubMed2000

NMR structure of oxidized glutaredoxin 3 from Escherichia coli.

A high precision NMR structure of oxidized glutaredoxin 3 [C65Y] from Escherichia coli has been determined. The conformation of the active site including the disulphide bridge is highly similar to those in glutaredoxins from pig liver and T4 phage. A comparison with the previously determined structure of glutaredoxin 3 [C14S, C65Y] in a complex with glutathione reveals conformational changes between the free and substrate-bound form which includes the sidechain of the conserved, active site tyrosine residue. In the oxidized form this tyrosine is solvent exposed, while it adopts a less exposed conformation, stabilized by hydrogen bonds, in the mixed disulfide with glutathione. The structures further suggest that the formation of a covalent linkage between glutathione and glutaredoxin 3 is necessary in order to induce these structural changes upon binding of the glutathione peptide. This could explain the observed low affinity of glutaredoxins for S-blocked glutathione analogues, in spite of the fact that glutaredoxins are highly specific reductants of glutathione mixed disulfides.

Amino Acid Sequence↗
PubMed2000

Perioperative cardiac function and predictors for adverse events after transmyocardial laser treatment.

BACKGROUND: Previous studies have reported that mortality and morbidity after transmyocardial laser treatment (TML) mainly occur perioperatively. The present study was designed to evaluate left-ventricular function and identify risk factors for cardiac-related adverse events in this phase. METHODS: Forty-nine patients were studied. The inclusion criteria were angina pectoris Canadian Cardiovascular Society Angina Score (CCSAS) class III and IV refractory to medical therapy and untreatable by coronary artery bypass graft or percutaneous transluminal coronary angioplasty, age less than 75 years, left ventricular ejection fraction greater than or equal to 30%, and myocardial regions with reversible ischemia. Hemodynamic data and cardiac adverse events were registered. The follow-up time was 30 days. RESULTS: A transient decrease in mean cardiac index (CI) was observed, reaching its minimum immediately after end of the surgical procedure (1.8+/-0.4, p<0.01 vs. baseline). Two patients (4%) died during the postoperative period (30 days). Seventeen patients (35%) experienced adverse cardiac-related events, where CCSAS class IV, unprotected left main stem stenosis, and diabetes mellitus were identified as risk factors in a multivariate analysis. CONCLUSIONS: A transient impairment of left ventricular function was observed after TML. The morbidity and mortality after TML were almost exclusively cardiac-related, identifying CCSAS class IV, unprotected left main stem stenosis, and diabetes as risk factors.

Aged↗
PubMed2000

Transmyocardial revascularization with CO2 laser in patients with refractory angina pectoris. Clinical results from the Norwegian randomized trial.

OBJECTIVES: The purpose of the study was to evaluate clinical effects, exercise performance and effect on maximal oxygen consumption (MVO2) of transmyocardial revascularization with CO2-laser (TMR) in patients with refractory angina pectoris. BACKGROUND: Transmyocardial laser revascularization is a new method to treat patients with refractory angina pectoris not eligible for conventional revascularization. Few randomized studies comparing TMR with conventional treatment have been published. METHODS: One hundred patients with refractory angina not eligible for conventional revascularization were block-randomized in a 1:1 ratio to receive continued optimal medical treatment (MT) or TMR in addition to MT. The patients were evaluated at baseline and at three and 12 months with end points to symptoms, exercise capacity and MVO2. RESULTS: Transmyocardial laser revascularization resulted in significant relief in angina symptoms after three and 12 months compared to baseline. Time to chest pain during exercise increased from baseline by 78 s after three months (p = NS) and 66 s (p < 0.01) after 12 months in the TMR group, whereas total exercise time and MVO2 were unchanged. No significant changes were observed in the MT group. Perioperative mortality was 4%. One year mortality was 12% in the TMR group and 8% in the MT group (p = NS.) CONCLUSIONS: Transmyocardial laser revascularization was performed with low perioperative mortality and caused significant symptomatic improvement, but no improvement in exercise capacity.

Adult↗
PubMed1999

[Transmyocardial laser treatment--a new treatment modality in pronounced angina pectoris?].

Transmyocardial laser treatment is currently being evaluated as a treatment modality for patients with severe coronary artery disease unsuitable for conventional revascularization with percutaneous transluminal coronary angioplasty or coronary artery bypass grafting. The original hypothesis was that laser-made channels could contribute to myocardial perfusion by conducting blood from the left ventricular cavity into the ischemic myocardium. Results from clinical trials suggest that transmyocardial laser treatment leads to a significant decrease in physician-assessed angina scores and improvement of quality of life. There are, however, conflicting data regarding the effect of myocardial perfusion, and the mechanisms responsible for the observed clinical effect remain unclear. It has been suggested that the angina relief is caused by destruction of myocardial peripheral nerve-endings and improved perfusion through induction of angiogenesis and collateral recruitment. A review of transmyocardial laser treatment with emphasis on experimental and clinical results, based on a thoroughly performed search on Medline of English language publications up until May 1999, is presented.

Angina Pectoris↗
PubMed1999

Direct NMR observation of the Cys-14 thiol proton of reduced Escherichia coli glutaredoxin-3 supports the presence of an active site thiol-thiolate hydrogen bond.

The active site of Escherichia coli glutaredoxin-3 (Grx3) consists of two redox active cysteine residues in the sequence -C11-P-Y-C14-H-. The 1H NMR resonance of the cysteine thiol proton of Cys-14 in reduced Grx3 is observed at 7.6 ppm. The large downfield shift and NOEs observed with this thiol proton resonance suggest the presence of a hydrogen bond with the Cys-11 thiolate, which is shown to have an abnormally low pKa value. A hydrogen bond would also agree with activity data of Grx3 active site mutants. Furthermore, the activity is reduced in a Grx3 H15V mutant, indicating electrostatic contributions to the stabilization of the Cys-11 thiolate.

Bacterial Proteins↗
PubMed1999

NMR structure of Escherichia coli glutaredoxin 3-glutathione mixed disulfide complex: implications for the enzymatic mechanism.

Glutaredoxins (Grxs) catalyze reversible oxidation/reduction of protein disulfide groups and glutathione-containing mixed disulfide groups via an active site Grx-glutathione mixed disulfide (Grx-SG) intermediate. The NMR solution structure of the Escherichia coli Grx3 mixed disulfide with glutathione (Grx3-SG) was determined using a C14S mutant which traps this intermediate in the redox reaction. The structure contains a thioredoxin fold, with a well-defined binding site for glutathione which involves two intermolecular backbone-backbone hydrogen bonds forming an antiparallel intermolecular beta-bridge between the protein and glutathione. The solution structure of E. coli Grx3-SG also suggests a binding site for a second glutathione in the reduction of the Grx3-SG intermediate, which is consistent with the specificity of reduction observed in Grxs. Molecular details of the structure in relation to the stability of the intermediate and the activity of Grx3 as a reductant of glutathione mixed disulfide groups are discussed. A comparison of glutathione binding in Grx3-SG and ligand binding in other members of the thioredoxin superfamily is presented, which illustrates the highly conserved intermolecular interactions in this protein family.

Amino Acid Sequence↗
PubMed1999

Is atrial fibrillation caused by extracorporeal circulation?

BACKGROUND: Atrial fibrillation is the most common rhythm disturbance encountered after open heart operations, with a reported incidence up to 40%. Despite its high incidence and clinical relevance its etiology remains obscure. It has been hypothesized that atrial fibrillation might be related to extracorporeal circulation. We performed a retrospective study (January 1, 1997 to December 31, 1997) comparing the incidence of atrial fibrillation in 3 groups of patients revascularized with and without extracorporeal circulation. METHODS: The first group comprised patients with coronary artery disease operated on with standard revascularization technique with cardiopulmonary bypass (n = 685). The second group included patients who had minimally invasive coronary artery bypass grafting without the use of extracorporeal circulation (n = 19). Patients in the third group had off-pump transmyocardial laser revascularization (n = 19). RESULTS: There was no significant difference in the incidence of atrial fibrillation in the group that had conventional coronary artery bypass and the group that had minimally invasive coronary artery bypass without cardiopulmonary bypass. The incidence of atrial fibrillation was significantly lower in the transmyocardial laser group compared with the other two groups. CONCLUSIONS: The present study found that postoperative atrial fibrillation is not caused solely by extracorporeal circulation, but patients who had transmyocardial laser revascularization had a significantly lower incidence of atrial fibrillation.

Aged↗
PubMed1998

Heteronuclear correlation experiments for the determination of one-bond coupling constants.

Spin-state selective experiments, HSQC-alpha/beta and CT-HMQC-alpha/beta, are proposed for the simple and rapid measurement of scalar one-bond coupling constants in two-dimensional, 1H-detected 15N-1H or 13C-1H correlation experiments based on HSQC and HMQC schemes. Pairs of subspectra are obtained, containing either the high-field or the low-field component of the doublet representing the one-bond coupling constant. The subspectral editing procedure retains the full sensitivity of HSQC and HMQC spectra recorded without heteronuclear decoupling during data acquisition, with a spectral resolution similar to that of decoupled spectra.

Bacterial Proteins↗
PubMed1998

Pulmonary intravascular macrophages appear in rats after long-term administration of lipid emulsion and amino acid solution. An ultrastructural morphometric study.

Intravascular macrophages have rarely been seen in normal lungs of humans and rats, but in rats endotoxaemia has induced their presence. To study whether substrates used for parenteral nutrition could have a similar stimulatory effect on mononuclear phagocytes, rats were given lipid emulsion (n=5), amino acid solution (n=5), or isotonic saline (n=5) through central venous catheters for 3 weeks. Structural changes in the lung microvessels were evaluated using electron microscopy. The areal fraction of pulmonary intravascular mononuclear phagocytes was 19.6% (SD=8.2) in rats given lipid emulsion (p<0.05) and 8.2% (SD=8.2) in rats given amino acid solution n.s. compared to 2.4% (SD= 4.0) in rats given saline. The increase in areal fraction was mainly due to an increase in cell numbers. In rats given lipid emulsion the intravascular phagocytes were only slightly larger than in rats given saline, but had the morphological features of mature macrophages. The study demonstrates that lipid emulsion recruits pulmonary intravascular macrophages in rats, indicating a stimulatory effect on the mononuclear phagocyte system. The effect was less pronounced with amino acid solution.

Amino Acids↗
PubMed1997

Retrograde internal mammary artery as coronary bypass. A prospective study with postoperative angiographic evaluation.

Although the internal mammary artery (IMA) as a coronary graft offers better long-term patency than the saphenous vein, a factor limiting its use has been the length of the artery's pedicle. In an attempt to overcome this limitation, we evaluated the use of retrograde right IMA in a prospective study. In ten patients scheduled for routine coronary artery bypass surgery, bilateral IMA grafting was used, the left IMA in routine fashion, but the right IMA dissected from the level of the first rib, cut there and placed as an inverted graft. Three months postoperatively the patients were clinically evaluated with stress exercise test (n = 10) and coronary angiography (n = 9). No patient had recurrence of angina. Angiography revealed patency of the retrograde right IMA graft in six of nine patients. On the basis of these data we do not recommend routine use of retrograde IMA.

Aged↗
PubMed1996

[Video-assisted heart surgery--an alternative in the future?].

Percutaneous angioplasty has been the procedure of choice for one- or two-vessel coronary artery disease because it is less invasive than open heart surgery. Video-assisted coronary artery bypass surgery, using the internal mammary artery, may be an alternative method which is also less invasive than conventional open heart surgery. A technique of video-assisted coronary bypass surgery is described. A limited incision is performed in the 4. intercostal space. The left anterior descending artery is pictured and inspected. A 30 degrees thoracoscope is introduced through a separate incision lateral to the thoracotomy. The dissection is performed and the cauterising instrument introduced through the thoracotomy. The anastomotic procedure is performed while the heart is beating and without extracorporeal circulation. The heart rate may be slowed down by administering a betablocking agent. The patient is extubated in the early postoperative period and mobilized in the same way as after conventional coronary artery bypass surgery.

Coronary Artery Bypass↗
PubMed1996

Glutaredoxin-3 from Escherichia coli. Amino acid sequence, 1H AND 15N NMR assignments, and structural analysis.

The primary and secondary structure of glutaredoxin-3 (Grx3), a glutathione-disulfide oxidoreductase from Escherichia coli, has been determined. The amino acid sequence of Grx3 consists of 82 residues and contains a redox-active motif, Cys-Pro-Tyr-Cys, typical of the glutaredoxin family. Sequence comparison reveals a homology (33% identity) to that of glutaredoxin-1 (Grx1) from E. coli as well as to other members of the thioredoxin superfamily. In addition to the active site cysteine residues, Grx3 contains one additional cysteine (Cys65) corresponding to one of the two non-active site (or structural) cysteine residues present in mammalian glutaredoxins. The sequence-specific 1H and 15N nuclear magnetic resonance assignments of reduced Grx3 have been obtained. From a combined analysis of chemical shifts, 3JHNalpha coupling constants, sequential and medium range NOEs, and amide proton exchange rates, the secondary structure of reduced Grx3 was determined and found to be very similar to that inferred from amino acid sequence comparison to homologous proteins. The consequences of the proposed structural similarity to Grx1 are that Grx3, while possessing a largely intact GSH binding cleft, would have a very different spatial distribution of charged residues, most notably surrounding the active site cysteine residues and occurring in the proposed hydrophobic protein-protein interaction area. These differences may contribute to the observed very low Kcat of Grx3 as a reductant of insulin disulfides or as a hydrogen donor for ribonucleotide reductase. Thus, despite an identical active site disulfide motif and a similar secondary structure and tertiary fold, Grx3 and Grx1 display large functional differences in in vitro protein disulfide oxido-reduction reactions.

Amino Acid Sequence↗
PubMed1996

Resonance assignment and structural analysis of acid denatured E. coli [U-15N]-glutaredoxin 3: use of 3D 15N-HSQC-(TOCSY-NOESY)-15N-HSQC.

Virtually complete sequence specific 1H and 15N resonance assignments are presented for acid denatured reduced E. coli glutaredoxin 3. The sequential resonance assignments of the backbone rely on the combined use of 3D F1-decoupled ROESY-15N-HSQC and 3D 15N-HSQC-(TOCSY-NOESY)-15N-HSQC using a single uniformly 15N labelled protein sample. The sidechain resonances were assigned from a 3D TOCSY-15N-HSQC and a homonuclear TOCSY spectrum. The presented assignment strategy works in the absence of chemical exchange peaks with signals from the native conformation and without 13C/15N double labelling. Chemical shifts, 3J(alpha H, NH) coupling constants and NOEs indicate extensive conformational averaging of both backbone and side chains in agreement with a random coil conformation. The only secondary structure element persisting at pH 3.5 appears to be a short helical segment comprising residues 37 to 40.

Amino Acid Sequence↗