A crystallographic comparison between mutated glyceraldehyde-3-phosphate dehydrogenases from Bacillus stearothermophilus complexed with either NAD+ or NADP+.

Mutations have been introduced in the cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Bacillus stearothermophilus in order to convert its cofactor selectivity from a specificity towards NAD into a preference for NADP. In the B-S mutant, five mutations (L33T, T34G, D35G, L187A, P188S) were selected on the basis of a sequence alignment with NADP-dependent chloroplastic GAPDHs. In the D32G-S mutant, two of the five mutations mentioned above (L187A, P188S) have been used in combination with another one designed from electrostatic considerations (D32G). Both mutants exhibit a dual-cofactor selectivity at the advantage of either NAD (B-S) or NADP (D32G-S). In order to analyse the cofactor-binding site plasticity at the molecular level, crystal structures of these mutants have been solved, when complexed with either NAD+ (D32G-Sn, resolution 2.5 A, R = 13.9%; B-Sn, 2.45 A, 19.3%) or NADP+ (D32G-Sp, 2.2 A, 19.2%; B-Sp, 2.5 A, 14.4%). The four refined models are very similar to that of the wild-type GAPDH and as expected resemble more closely the holo form than the apo form. In the B-S mutant, the wild-type low affinity for NADP+ seems to be essentially retained because of repulsive electrostatic contacts between the extra 2'-phosphate and the unchanged carboxylate group of residue D32. Such an antideterminant effect is not well compensated by putative attractive interactions which had been expected to arise from the newly-introduced side-chains. In this mutant, recognition of NAD+ is slightly affected with respect to that known on the wild-type, because mutations only weakly destabilize hydrogen bonds and van der Waals contacts originally present in the natural enzyme. Thus, the B-S mutant does not mimic efficiently the chloroplastic GAPDHs, and long-range and/or second-layer effects, not easily predictable from visual inspection of three-dimensional structures, need to be taken into account for designing a true "chloroplastic-like" mutant of cytosolic GAPDH. In the case of the D32G-S mutant, the dissociation constants for NAD+ and NADP+ are practically reversed with respect to those of the wild-type. The strong alteration of the affinity for NAD+ obviously proceeds from the suppression of the two wild-type hydrogen bonds between the adenosine 2'- and 3'-hydroxyl positions and the D32 carboxylate group. As expected, the efficient recognition of NADP+ is partly promoted by the removal of intra-subunit electrostatic repulsion (D32G) and inter-subunit steric hindrance (L187A, P188S). Another interesting feature of the reshaped NADP+-binding site is provided by the local stabilization of the extra 2'-phosphate which forms a hydrogen bond with the side-chain hydroxyl group of the newly-introduced S188. When compared to the presently known natural NADP-binding clefts, this result clearly demonstrates that an absolute need for a salt-bridge involving the 2'-phosphate is not required to switch the cofactor selectivity from NAD to NADP. In fact, as it is the case in this mutant, only a moderately polar hydrogen bond can be sufficient to make the extra 2'-phosphate of NADP+ well recognized by a protein environment.

The crystal structure of d-glyceraldehyde-3-phosphate dehydrogenase from the hyperthermophilic archaeon Methanothermus fervidus in the presence of NADP(+) at 2.1 A resolution.

The crystal structure of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from the archaeon Methanothermus fervidus has been solved in the holo form at 2.1 A resolution by molecular replacement. Unlike bacterial and eukaryotic homologous enzymes which are strictly NAD(+)-dependent, GAPDH from this organism exhibits a dual-cofactor specificity, with a marked preference for NADP(+) over NAD(+). The present structure is the first archaeal GAPDH crystallized with NADP(+). GAPDH from M. fervidus adopts a homotetrameric quaternary structure which is topologically similar to that observed for its bacterial and eukaryotic counterparts. Within the cofactor-binding site, the positively charged side-chain of Lys33 decisively contributes to NADP(+) recognition through a tight electrostatic interaction with the adenosine 2'-phosphate group. Like other GAPDHs, GAPDH from archaeal sources binds the nicotinamide moiety of NADP(+) in a syn conformation with respect to the adjacent ribose and so belongs to the B-stereospecific class of oxidoreductases. Stabilization of the syn conformation is principally achieved through hydrogen bonding of the carboxamide group with the side-chain of Asp171, a structural feature clearly different from what is observed in all presently known GAPDHs from bacteria and eukaryotes. Within the catalytic site, the reported crystal structure definitively confirms the essential role previously assigned to Cys140 by site-directed mutagenesis studies. In conjunction with new mutation results reported in this paper, inspection of the crystal structure gives reliable evidence for the direct implication of the side-chain of His219 in the catalytic mechanism. M. fervidus grows optimally at 84 degrees C with a maximal growth temperature of 97 degrees C. The paper includes a detailed comparison of the present structure with four other homologous enzymes extracted from mesophilic as well as thermophilic organisms. Among the various phenomena related to protein thermostabilization, reinforcement of electrostatic and hydrophobic interactions as well as a more efficient molecular packing appear to be essentially promoted by the occurrence of two additional alpha-helices in the archaeal GAPDHs. The first one, named alpha4, is located in the catalytic domain and participates in the enzyme architecture at the quaternary structural level. The second one, named alphaJ, occurs at the C terminus and contributes to the molecular packing within each monomer by filling a peripherical pocket in the tetrameric assembly.

17O NMR and FT-IR study of the ionization state of peptides in aprotic solvents. Application to Leu-enkephalin.

The ionization state of Leu-enkephalin in DMSO and MeCN/DMSO (4/1) solution was studied by the combined use of 17O NMR and FT-IR spectroscopy. After lyophilization of an aqueous solution at nearly neutral pH, Leu-enkephalin essentially exists in the uncharged state in MeCN/DMSO (4/1) solution. In pure DMSO, only 40% of the Leu-enkephalin molecules are in the zwitterionic state under the same conditions.

Results of percutaneous mitral commissurotomy in 200 patients.

To assess the feasibility and efficacy of percutaneous mitral commissurotomy (PMC), the procedure was attempted in 200 patients with severe mitral stenosis. There were 154 women and 46 men, their mean age was 43 +/- 16 years (range 13 to 79) and 15 were older than 70 years of age. Forty-four had had previous surgical commissurotomy. Forty were in New York Heart Association class II, 152 in class III and 8 in class IV. In regard to valvular anatomy, 67 had calcified valves, 58 had pliable valves and only mild subvalvular disease, and 75 had flexible valves but extensive subvalvular disease. Grade 1+ mitral regurgitation was present in 62 and grade 2+ in 2. In 11 patients the procedure was discontinued because of complications in 3 and technical failure in 8. Six of the 8 technical failures occurred during the first 15 attempts. Effective PMC was performed in 189 patients using 1 balloon in 23 and 2 balloons in 166. After PMC, there was a significant improvement in mean left atrial pressure (21 +/- 7 to 12 +/- 5 mm Hg, p less than 0.0001), mean mitral gradient (16 +/- 6 to 6 +/- 2 mm Hg, p less than 0.0001), cardiac index (2.6 +/- 0.8 to 3.1 +/- 0.8 liters/min/m2, p less than 0.001) and valve area assessed by hemodynamics (1.1 +/- 0.3 to 2.2 +/- 0.5 cm2, p less than 0.0001) and 2-dimensional echocardiography (1 +/- 0.3 to 1.9 +/- 0.4 cm2, p less than 0.0001). No patient died. Embolism occurred in 8 (4%), with no further sequelae. Sixteen (8%) had atrial septal defect detected by oxymetry.(ABSTRACT TRUNCATED AT 250 WORDS)

[Doppler measurement of transvalvular gradients. Simultaneous Doppler-catheterization recordings on 78 patients]. / Mesure des gradients transvalvulaires par le Doppler. Enregistrements simultanés Doppler-cathétérisme chez 78 patients.

Several studies have demonstrated the value of Doppler ultrasound as a means of measuring gradients across cardiac valves. However, in view of sudden variations in cardiac output gradients should be measured simultaneously by Doppler and catheterization in order to validate the former method and determine its accuracy. We conducted a prospective study with simultaneous recordings in 78 patients with aortic valve stenosis (33) or mitral valve stenosis (19) or cardiac valve prosthesis (26). Mean age of the patients was 55 +/- 14 years, and 50% of them were male. Subjects with pure or predominant regurgitation were excluded from the study. In the whole of the population studied, correlation between Doppler ultrasound and haemodynamics was very good with r = 0.98, p less than 0.001 for maximum gradient and r = 0.96, p less than 0.001 for mean gradient. The perfect simultaneity of the haemodynamic and ultrasonic recordings was confirmed by comparing the duration of gradients measured by the two methods (r = 0.996, p less than 0.001). There also was very close correlation between ultrasounds and catheter in patients with mitral stenosis (maximum gradient r = 0.98, p less than 0.001; mean gradient r = 0.97, p less than 0.001). Mean Doppler-catheter differences were not significant, and no underestimation by Doppler reached or exceeded 5 mmHg. Correlations were also satisfactory in patients with aortic stenosis (maximum gradient r = 0.97, p less than 0.01; mean gradient r = 0.90, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Percutaneous mitral commissurotomy. Apropos of 130 cases]. / La commissurotomie mitrale percutanée. A propos de 130 cas.

In order to evaluate the effectiveness and risks of percutaneous mitral commissurotomy (PMC), we tried this procedure in 130 patients. Nine attempts were unsuccessful due to pre-PMC complications (haemopericardium 2, air embolism 1) or to technical failure (6 cases, 5 of which occurred in the first 15 attempts). PMC could be performed in 121 patients: 88 women and 33 men aged from 13 to 79 years (mean 42 + 15 years); 22 patients had previously been operated upon, 5 had a history of embolism, 99 were in functional stage III or IV. Echocardiography divided these patients into 3 groups: 29 had calcified leaflets (group 1), 42 had flexible leaflets and little alteration of the subvalvar system (group 2), and 49 had flexible leaflets with alteration of the subvalvar system (group 3). Mitral regurgitation grade 1/4 was present in 32 cases. PMC was performed with one balloon (Trefoil 3 x 12 mm) in 14 patients and therafter with two balloons (Trefoil 3 x 10 mm plus conventional 15 or 19 mm balloon) in 107 patients. PMC resulted in significant improvement in haemodynamic values: the mean capillary pressure fell from 20 +/- 7 to 11 +/- 5 mmHg (p less than 0.0001) and the mean mitral gradient from 16 +/- 6 to 6 +/- 2 mmHg (p less than 0.0001), while the cardiac index rose from 2.7 +/- 0.6 to 3.1 +/- 0.7 l/mn/m2 (p less than 0.001) and the mitral valve area (MVA) from 1.1 +/- 0.2 to 2.2 +/- 0.5 cm2 (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation by two-dimensional and doppler echocardiography of the results of percutaneous mitral valvuloplasty]. / Evaluation par échographie bidimensionnelle et doppler des résultats de la valvuloplastie mitrale percutanée.

The purpose of this study was to determine the value of two-dimensional echocardiography and doppler ultrasound in the evaluation of the results and mechanism of percutaneous mitral valvuloplasty. The study involved 200 patients (77 p. 100 female) of mean age 43 +/- 15 years (range 13 to 79 years), most of whom were in NYHA class III or IV. The patients were divided into three groups according to the severity of the anatomical lesions. Group I patients (n = 58) had flexible valves and only minor alterations of the subvalvular structures; group II patients (n = 75) had flexible valves but deeply altered subvalvular structures; group III patients (n = 67) had calcified valves. Following valvuloplasty, the mean transmitral doppler gradient fell from 16 to 5 mmHg (p less than 0.0001) and the mitral valve area, as measured by two-dimensional echocardiography, increased from 1 to 1.9 cm2 (p less than 0.00001); the corresponding values at doppler measurement were 1 and 2 cm2 respectively. In patients successfully dilated, two-dimensional echocardiography showed that the mechanism involved was complete opening of one or both commissures. Before dilatation, 68 patients (34 p. 100) had an usually small degree of mitral regurgitation. After dilatation, grade 3/4 mitral regurgitation was observed in 9 patients (4.5 p. 100). The quality of the results obtained depended on the anatomical lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

[Echography in surgical mitral insufficiency. Pathologic diagnosis and provision of the surgical procedure]. / L'échographie des insuffisances mitrales chirurgicales. Diagnostic lésionnel et prévision du type de chirurgie.

The aim of this study was to determine the reliability of preoperative transthoracic and transesophageal echocardiography compared with the surgical findings in pure or dominant severe mitral regurgitation with respect to: the evaluation of the lesions, mechanism and etiology; the provision of the type of surgery (valve replacement or reconstruction); One hundred and fifty patients were divided into two groups: Group I (N = 120) in which preoperative assessment included transthoracic echo-Doppler coupled with color Doppler in the last 32 patients; Group II (N = 30) operated recently who underwent both transesophageal and transthoracic echo-Doppler examination. In Group I, the sensitivity of transthoracic echo in the evaluation of the etiological was 86% overall [100% in rheumatic valve disease (N = 28), 86% in degenerative or dystrophic valves (N = 72), 44% in endocarditis (N = 9), 87% in ischaemic dysfunction (N = 8)]. The echo evaluation of the mechanism of the regurgitation was also reliable with the exception of ruptured chordae in which direct visualisation of the rupture was only possible in 19 of the 64 cases (30%). The type of surgery predicted by echo was practiced in 87% of cases.

[Value of transesophageal echocardiography. From a preliminary experience of 532 cases]. / Intérêt de l'échographie cardiaque par voie transoesophagienne. A partir d'une expérience préliminaire de 532 cas.

Transesophageal echocardiography (TEE) was introduced recently in France. The aim of this study was to review the diagnostic value of this technique after 8 months' use in our cardiology department. A total of 532 TEE studies were carried out between April and December 1988 in 396 patients (average age 54 years, range 17 to 89 years) at Tenon Hospital. The failure rate was 1.8 per cent (N = 10), over half of which occurred at the beginning of the operator's experience. TEE was particularly valuable compared with the standard transthoracic approach in the following instances: the investigation of mitral stenosis, especially before percutaneous valvuloplasty (N = 75). A left atrial thrombus was demonstrated in 5 cases by TEE vs none by standard echocardiography. There was also a much higher diagnostic sensitivity for small interatrial shunts (40 vs 6) resulting from transseptal catheterisation. In the preoperative investigation of severe mitral regurgitation (N = 29). The etiology was accurately diagnosed in 29 vs 26 cases, and the mechanism of the regurgitation was correctly classified especially in cases of ruptured chordae (15 vs 6 cases). In endocarditis (N = 26) by the visualisation of abscess of the aortic ring (7 vs 1) and vegetations (19 vs 8). In prosthetic valve dysfunction (N = 65) by the demonstration of primary degeneration of bioprostheses (7 vs 4), perivalvular leaks (10 vs 4) and non-occlusive thrombi of mechanical prostheses (3 vs 0). In cases of intracardiac tumours, dissection of the thoracic aorta and atrial septal defects.(ABSTRACT TRUNCATED AT 250 WORDS)

[Björk-Shiley-Monostrut prosthesis of the aortic valve. Mid-term development]. / Prothèse de Björk-Shiley-Monostrut en position aortique. Evolution à moyen terme.

From July 84 to June 88, 100 patients underwent an isolated aortic valve replacement by a Monostrut-Björk-Shiley prosthesis. Fifty-one had calcified aortic stenosis, 24% aortic insufficiency, 25% mixed aortic lesions. Pre-operatively, their mean age was 57 years, 68% were male, 46% were in NYHA class II or IV, 43% had angina, all were in sinus rhythm. Operative mortality was 4%. All the survivors were followed-up for a mean period of 22 months (6 to 58) with a cumulative follow-up of 183 patients-years. All patients were placed on a long-term regimen of anticoagulant therapy. Two late deaths occurred (1 myocardial infarction, 1 cerebral hemorrhage). The 4 years survival rate was 94%. Postoperative functional results were excellent. Nearly all patients were asymptomatic. Concerning valve related complications: the 4 years actuarial rate of patients free from thromboembolism, hemorrhage, valve thrombosis, periprosthetic leakage and endocarditis were respectively 97%, 97%, 100%, 100% and 100%. No patient were reoperated on. Valvular function was evaluated by mean transprothetic gradient on echo-doppler (61 cases) and by the calculation of the valvular area with transseptal catheterization (21 cases). For small sizes prosthesis (annulus diameter of 19 or 21 mm), medium size prosthesis (23 or 25 mm), large size prosthesis (27 to 29 mm), mean transprothetic gradient were respectively 16, 10 and 6.9 mmHg and valvular aortic area were respectively 1.5, 1.9 and 2.4 cm2. Mid term results of the Monostrut-Björk-Shiley prosthesis on aortic position are good with a low rate of valve related complications and good hemodynamic results, even with the small valve size.

[Eisenmenger syndrome and pregnancy. Apropos of a case]. / Syndrome d'Eisenmenger et grossesse. A propos d'un cas.

A case of Eisenmenger syndrome associated with an ongoing pregnancy and maternal death one month after cesarean section is reported. The review of the world literature shows the very high maternal risk of this condition, which should be prevented by tubal sterilization or therapeutic abortion in the very early pregnancy.

N-Methyl peptides. IV. Water and beta-turn in peptides. Crystal structure of N-pivaloyl-L-prolyl-N,N'-dimethyl-D-alaninamide in the anhydrous and monohydrated states.

The model tripeptide tBuCO-L-Pro-Me-D-Ala-MHMe crystallizes in both anhydrous (1) and monohydrated (2) states: 1, monoclinic space group C2 with a = 20.030 (2) A, b = 5.836 (2) A, c = 14.958 (3) A and beta = 94.11 (1) degrees; 2, orthorhombic space group P212121 with a = 6.971 (6) A, b = 11.766 (3) A, and c = 22.394 (8) A. Both crystal structures were solved by X-ray diffraction in order to characterize the influence of water on the molecular structure. The anhydrous molecule accommodates the well-known, beta II-folded conformation with three trans amide functions and an intramolecular i + 3 leads to hydrogen bond. In the hydrated molecule, water is inserted in a loop containing 12 atoms and induces some conformational changes of the peptide backbone.

Conformational perturbations in retro-analogs of the tBuCO-Ala-Gly-NHiPr dipeptide. Crystal structure of the retro-dipeptide with a reversed Ala-Gly amide bond.

The three retro-analogs of the tBuCO-Ala-Gly-NHiPr dipeptide, in which each amide bond had been successively reversed, were studied in solution by 1H-n.m.r. and i.r. spectroscopy with reference to the conformational properties of their parent dipeptide. Reversal of the Ala-Gly amide bond proved to perturb the folding tendency of the backbone less than the inversion of either of the terminal amide bonds. The crystal structure of the retro-peptide containing a reversed Ala-Gly amide bond was also solved by X-ray diffraction and constitutes the first available data for this retro-peptide series. In contrast to the beta II-folded structure of the parent dipeptide, the retro-peptide molecule adopts an open conformation in the crystal.

[Transesophageal echography. Value of the technic apropos of a preliminary experiment in 320 patients (385 examinations)]. / L'échographie par voie oesophagienne. Intérêt de la technique à propos d'une expérience préliminaire concernant 320 patients (385 examens)

The authors discuss the clinical utility and feasibility of trans-esophageal echocardiography. Between April and October 1988, 385 examinations were performed in 320 patients (mean age: 54 yr, range: 17-89). In 9 patients (2.4 p. 100), the transesophageal transducer could not be introduced. The only complication was one case of bacteremia without sequela, that occurred early in our use of this technique. Transesophageal echocardiography proved to be useful in the following indications: mitral stenosis (n = 50), mainly by detecting thromboses of the left atrium (n = 5); infectious endocarditis (n = 21), especially for diagnosing aortic ring abscesses (n = 3); severe mitral insufficiency (n = 26), to assess the mechanism of regurgitation and to visualize chordal rupture (n = 13). We conclude from this preliminary study that transesophageal echocardiography is particularly useful in the pathologies described above as a complementary procedure to conventional echocardiography.

Structure of tBuCO-Val psi [NH-CO]NHtBu.

N-Isobutylidenedipivalamide, C14H28N2O2, Mr = 256.39, orthorhombic, P2(1)2(1)2(1), a = 16.656 (2), b = 9.751 (2), c = 10.583 (2) A, V = 1718.8 A3, Z = 4, D chi = 0.99 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 4.56 cm-1, mu Rmax much less than 1, F(000) = 568, T = 293 K, R = 0.081 for 887 observed reflections. The geometrical parameters of this retro-peptide molecule are quite similar to the standard values for peptides. Conformational angles are phi = -101 (1), phi' = 99 (1) degrees.

Structure of MeCO-Gly psi [NH-CO]NHMe.

N,N'-Methylenediacetamide, C5H10N2O2, Mr = 130.15, orthorhombic, Pna2(1), a = 17.218 (1), b = 4.489 (1), c = 18.124 (1) A, V = 1400.8 A3, Z = 8, D chi = 1.23 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu Rmax much less than 1, mu = 7.19 cm-1, F(000) = 560, T = 293 K, R = 0.044 for 1318 observed reflections. This retro-peptide molecule assumes two nearly identical conformational states (A phi = 93.2, phi' = 77.0; B phi = 90.6, phi' = 79.6 degrees) with planar trans amide functions. The bond lengths and bond angles are very close to the standard dimensions of the peptide group.

Structure of MeCO-psi[NH-CO]Val-NHMe.

N,N'-Dimethylisopropylmalonamide, C8H16N2O2, Mr = 172.23, orthorhombic, Pbcm, a = 4.859 (1), b = 13.523 (2), c = 15,469 (2) A, V = 1016.4 A3, Z = 4, Dx = 1.12 g cm-3, lambda(Cu K alpha) = 1.5418 A, microRmax much less than 1, mu = 5.88 cm-1, F(000) = 376, T = 293 K, R = 0.060 for 665 observed reflections. Dimensions of this retropeptide molecule are quite similar to the standard values for peptides. The C alpha and C beta atoms are in a mirror (z = 1/4), so conformational angles are psi' = -psi = -110.4 degrees (2).

Biological activities and structural properties of the atypical bacteriocins mesenterocin 52b and leucocin b-ta33a.

The antibacterial spectra and modes of action of synthetic peptides corresponding to mesenterocin 52B and leucocin B-TA33a greatly differ despite their high sequence homology. Circular dichroism experiments establish the capacity of each of these two peptides to partly fold into an amphiphilic helix that might be crucial for their adsorption at lipophilic-hydrophilic interfaces.

Phosphorus-31 nuclear magnetic resonance studies on coenzyme binding and specificity in glyceraldehyde-3-phosphate dehydrogenase.

Binding of NAD(P)+ to wild type and a series of mutants of the glycolytic NAD-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Bacillus stearothermophilus designed to alter the cofactor specificity [Clermont, S., Corbier, C., Mely, Y., Gerard, D., Wonacott, A., & Branlant, G. (1993) Biochemistry 21, 10178-10184] has been studied by 31P NMR. In the mutants with the L187A and P188S substitutions, the pyrophosphate signals are split, and the upfield resonance has been assigned to the P(a) phosphate. Titration of the NADP+ 2'-phosphate pKa deduced from its chemical shift shows that the electrostatic environment in the binding site is largely affected by the single point mutations. pKas ranging from 7.7 for the L187A-P188S mutant to < 5.7 for the D32G-L187A-P188S and D32A-L187A-P188S mutants have been observed, thus indicating that the binding of NADP+ is modulated by the ionization state of its 2'-phosphate. In the quintuple mutant L33T-T34G-D35G-L187A-P188S, designed in comparison with the photosynthetic NAD(P)-dependent GAPDH of the chloroplast, the 2'-phosphate has a pKa of 6.8. As further stabilizing interactions like hydrogen bonds or positively charged side chains would lower this pKa, it is suggested that the 2'-phosphate ionization state of bound NADP+ in chloroplastic GAPDH is dianionic. The NADP+ dissociation rate constants (k(off)) of the three mutants D32G, L187A-P188S, and D32G-L187A-P188S, are higher at pH 6.1 than at pH 8.1 and are similar at the same pH, indicating that the difference in binding affinity between these three mutants results from the molecular recognition step or conformational change upon binding.