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M R Conte

Publications and source records attributed to M R Conte.

At least 19 recordsLinked to original sources
PubMed2000

Structure of tandem RNA recognition motifs from polypyrimidine tract binding protein reveals novel features of the RRM fold.

Polypyrimidine tract binding protein (PTB), an RNA binding protein containing four RNA recognition motifs (RRMs), is involved in both pre-mRNA splicing and translation initiation directed by picornaviral internal ribosome entry sites. Sequence comparisons previously indicated that PTB is a non-canonical RRM protein. The solution structure of a PTB fragment containing RRMs 3 and 4 shows that the protein consists of two domains connected by a long, flexible linker. The two domains tumble independently in solution, having no fixed relative orientation. In addition to the betaalphabetabetaalphabeta topology, which is characteristic of RRM domains, the C-terminal extension of PTB RRM-3 incorporates an unanticipated fifth beta-strand, which extends the RNA binding surface. The long, disordered polypeptide connecting beta4 and beta5 in RRM-3 is poised above the RNA binding surface and is likely to contribute to RNA recognition. Mutational analyses show that both RRM-3 and RRM-4 contribute to RNA binding specificity and that, despite its unusual sequence, PTB binds RNA in a manner akin to that of other RRM proteins.

Amino Acid Motifs↗
PubMed2000

Microvascular angina (cardiological syndrome X) per se is not associated with hyperinsulinaemia or insulin resistance.

BACKGROUND: Microvascular angina has been found to be associated with insulin resistance. However, many factors known to affect insulin sensitivity were not excluded in patient selection. We aimed to evaluate whether microvascular angina is per se associated with insulin resistance. MATERIALS AND METHODS: We performed a Frequently Sampled Intravenous Glucose Tolerance Test (0.33 g kg(-1) b.w.) in 10 normal weight and normotensive patients with microvascular angina, with normal glucose tolerance and normal plasma lipids. Ten healthy subjects, comparable for age, sex, body mass index, blood pressure and plasma lipids, were used as control group. RESULTS: Fasting serum glucose (4.49+/-0.2 SEM vs. 4.52+/-0.13 mmol L(-1), P = 0.9), insulin (39.46 +/-3.68 SEM vs. 47.12+/-4.6 pmol L(-1), P = 0.21) and C-peptide (0.56 +/-0.05 SEM vs. 0.53+/-0.05 nmol L(-1), P = 0. 68) values, as well as estimated parameters of insulin secretion and hepatic insulin extraction were similar in the two groups. Insulin sensitivity values (median, range) were also similar in the patients and control subjects (5.76 (3.39-12.30) vs. 7.54 (3.68-13.89. 10(-4) x min(-1)/(microU/mL), P = 0.97). CONCLUSION: Microvascular angina per se is not associated with hyperinsulinaemia or insulin resistance when other confounding factors are excluded in patient selection.

Adult↗
PubMed1999

Infective endocarditis in hypertrophic cardiomyopathy: prevalence, incidence, and indications for antibiotic prophylaxis.

BACKGROUND: The literature on infective endocarditis in hypertrophic cardiomyopathy (HCM) is virtually confined to case reports. Consequently, the risk of endocarditis in HCM remains undefined. METHODS AND RESULTS: We assessed the occurrence of endocarditis in 810 HCM patients evaluated between 1970 and 1997. Endocarditis was diagnosed in 10 patients, 2 of whom were excluded from analysis of prevalence and incidence because they were referred for acute endocarditis. At first evaluation, echocardiographic features consistent with prior endocarditis were identified in 3 of 808 patients, a prevalence of 3.7 per 1000 patients (95% CI, 0.8 to 11). Of 681 patients who were followed, 5 developed endocarditis, an incidence of 1.4 per 1000 person-years (95% CI, 0.5 to 3.2); outflow obstruction was present in each of these 5 patients and was associated with the risk of endocarditis (P=0.006). In the 224 obstructive patients, incidence of endocarditis was 3.8 per 1000 person-years (95% CI, 1.6 to 8.9) and probability of endocarditis 4. 3% at 10 years. Left atrial size was also associated with the risk of endocarditis (P=0.007). In patients with both obstruction and atrial dilatation (>/=50 mm), incidence of endocarditis increased to 9.2 per 1000 person-years (95% CI, 2.5 to 23.5). Analysis of all 10 patients with endocarditis identified outflow obstruction in each and atrial dilatation in 7. CONCLUSIONS: Endocarditis in HCM is virtually confined to patients with outflow obstruction and is more common in those with both obstruction and atrial dilatation. These results indicate that antibiotic prophylaxis is required only in patients with obstructive HCM.

Acute Disease↗
PubMed1999

Subacute left ventricular free-wall rupture in early course of acute myocardial infarction. Clinical report of two cases and review of the literature.

Left ventricular free wall rupture (LVFWR) may complicate an acute myocardial infarction (AMI); its frequency ranges from 1 to 6 percent. In the era of coronary care units, LVFWR is the second cause of in-hospital death, after pump failure. The subacute presentation accounts for 2-3 percent of total hospital admissions for AMI. Heart rupture may not be suddenly fatal and sometimes there is enough time for surgical repair. Electromechanical dissociation is neither the only nor the main clinical presentation. More subtle symptoms occurring hours or days before the final event include unexplained hypotension and transient bradycardia and some ECG features such as persistent ST-segment elevation with T-waves failing to invert in the same leads. On echocardiographic subcostal view, pericardial effusion of more than 5-10 mm, with echo-dense masses overlying the heart independently of cardiac tamponade, is highly suggestive of heart rupture. If pericardiocentesis yields hemorrhagic fluid, surgical intervention is mandatory, providing both diagnostic confirmation and definitive treatment. Medical management strategies (prolonged bed rest, beta-blockade therapy) are still experimental but could become suitable for particular subsets of patients (elderly patients and patients at a high surgical risk). We report two cases of subacute LVFWR and review the currently available literature.

Aged↗
PubMed1998

Fixed subaortic stenosis associated with hypertrophic cardiomyopathy: report of a rare familial occurrence.

INTRODUCTION: Fixed subaortic stenosis is considered to be an acquired condition. It is often associated with congenital heart disease, creating a turbulence in the left ventricle outflow tract. Familial forms of fixed subaortic stenosis are very unusual. We report a remarkable familial cluster in which fixed subaortic stenosis is associated with hypertrophic cardiomyopathy. METHODS: Fourteen relatives of a patient affected with hypertrophic cardiomyopathy and fixed subaortic stenosis underwent cardiological examination, electrocardiogram and echo-doppler study. RESULTS: Two of the proband's sisters showed an association between asymmetrical hypertrophic cardiomyopathy and fixed subaortic stenosis. The brother presented a subaortic ridge and concentric left ventricular hypertrophy. The other members of the family (another brother and the third-generation relatives) were unaffected. CONCLUSIONS: While the association between fixed subaortic stenosis and hypertrophic cardiomyopathy has commonly been reported, there is little in the literature to suggest the family-related nature of this association. The familial occurrence of this association reveals genetic transmission, with a recessive autosomal pattern of inheritance. This finding goes against the usual autosomal dominant pattern of inheritance in hypertrophic cardiomyopathy. Familial studies of FSS are needed in order to gain a better understanding of the genetic background of these patients.

Aged↗
PubMed1997

The three-dimensional solution structure of the matrix protein from the type D retrovirus, the Mason-Pfizer monkey virus, and implications for the morphology of retroviral assembly.

The Mason-Pfizer monkey virus (M-PMV) is the prototype of the type D retroviruses. In type B and D retroviruses, the Gag protein pre-assembles before association with the membrane, whereas in type C retroviruses (lentiviruses, BLV/HTLV group) Gag is targeted efficiently to the plasma membrane, where the particle formation occurs. The N-terminal domain of Gag, the matrix protein (MA), plays a critical role in determining this morphogenic difference. We have determined the three-dimensional solution structure of the M-PMV MA by heteronuclear nuclear magnetic resonance. The protein contains four alpha-helices that are structurally similar to the known type C MA structures. This similarity implies possible common assembly units and membrane-binding mechanisms for type C and B/D retroviruses. In addition to this, the interpretation of mutagenesis data has enabled us to identify, for the first time, the structural basis of a putative intracellular targeting motif.

Cell Membrane↗
PubMed1997

Solution structure of the ATF-2 recognition site and its interaction with the ATF-2 peptide.

The effect of leucine zipper proteins binding to the DNA recognition site is controversial. Results from crystallography, gel and solution methods have led to opposite conclusions about the conformation of the DNA in the complex. The role of the DNA binding site in the recognition process and in the gene induction mediated by transcription factors needs to be investigated further. In this article the self-complementary 16 bp oligodeoxynucleotide (CATGTGACGTCACATG)2, which contains the cAMP response element recognised by numerous transcription factors of the leucine zipper family, has been examined free from proteins and in its interaction with the mammalian activating transcription factor 2. The recognition process has been investigated by circular dichroism analysis, which has revealed conformational changes in both DNA and protein upon binding. The solution structure of the 16mer, important in order to define the effects induced by binding of leucine zipper proteins and the intrisic bending properties of DNA, has been determined from NMR data using direct refinement against NOE intensities, analysis of scalar coupling constants and restrained molecular dynamics calculations. Final structures starting from the A and B forms of DNA agreed to a pairwise root mean square deviation (r.m.s.d.) of 1.04 +/- 0.3 A (0.7 +/- 0.2 A to the average) for all atoms. The terminal base pairs were less well determined, and the pairwise deviation of the 12 core bp was 0.83 +/- 0.27 A (0.55 +/- 0.19 A to the average). The final structures are within the B-family with an average helical twist of 36+/-2 degrees. No significant intrinsic DNA bend is shown in the activating transcription factor regulatory site. However, there are substantial deviations from the canonical B-DNA (r.m.s.d. = 3.6 A) in the core of the molecule, associated with relatively large base inclinations.

Activating Transcription Factor 2↗
PubMed1997

Conformational properties and thermodynamics of the RNA duplex r(CGCAAAUUUGCG)2: comparison with the DNA analogue d(CGCAAATTTGCG)2.

The thermodynamic stability of nine dodecamers (four DNA and five RNA) of the same base composition has been compared by UV-melting. TheDeltaG of stabilisation were in the order: r(GACUGAUCAGUC)2>r(CGCAAATTTGCG)2 approximately r(CGCAUAUAUGCG)2>d(CGCAAATTTGCG)2 approximately r(CGCAAAUUUGCG)2>d(CGCATATATGCG)2 approximately d(GACTGATCAGTC)2>r(CGCUUUAAAGCG)2 approximately d(CGCTTTAAAGCG)2. Compared with the mixed sequences, both r(AAAUUU) and r(UUUAAA) are greatly destablising in RNA, whereas in DNA, d(TTTAAA) is destabilising but d(AAATTT) is stabilising, which has been attributed to the formation of a special B'structure involving large propeller twists of the A-T base pairs. The solution structure of the RNA dodecamer r(CGCAAAUUUGCG)2has been determined using NMR and restrained molecular dynamics calculations to assess the conformational reasons for its stability in comparison with d(CGCAAATTTGCG)2. The structures refined to a mean pairwise r.m.s.d. of 0.89+/-0.29 A. The nucleotide conformations are typical of the A family of structures. However, although the helix axis displacement is approximately 4.6 A into the major groove, the rise (3.0 A) and base inclination ( approximately 6 degrees ) are different from standard A form RNA. The extensive base-stacking found in the AAATTT tract of the DNA homologue that is largely responsible for the higher thermodynamic stability of the DNA duplex is reduced in the RNA structure, which may account for its low relative stability.

Base Composition↗
PubMed1996

Hydration of the RNA duplex r(CGCAAAUUUGCG)2 determined by NMR.

The so-called spine of hydration in the minor groove of AnTn tracts in DNA is thought to stabilise the structure, and kinetically bound water detected in the minor groove of such DNA species by NMR has been attributed to a narrow minor groove [Liepinsh, E., Leupin, W. and Otting, G. (1994) Nucleic Acids Res. 22, 2249-2254]. We report here an NMR study of hydration of an RNA dodecamer which has a wide, shallow minor groove. Complete assignments of exchangeable protons, and a large number of non-exchangeable protons in r(CGCAAAUUUGCG)2 have been obtained. In addition, ribose C2'-OH resonances have been detected, which are probably involved in hydrogen bonds. Hydration at different sites in the dodecamer has been measured using ROESY and NOESY experiments at 11.75 and 14.1 T. Base protons in both the major and minor grooves are in contact with water, with effective correlation times for the interaction of approximately 0.5 ns, indicating weak hydration, in contrast to the hydration of adenine C2H in the homologous DNA sequence. NOEs to H1' in the minor groove are consistent with hydration water present that is not observed in the analogous DNA sequence. Hydration kinetics in nucleic acids may be determined by chemical factors such as hydrogen-bonding more than by simple conformational factors such as groove width.

Base Sequence↗
PubMed1996

Determination of sugar conformations by NMR in larger DNA duplexes using both dipolar and scalar data: application to d(CATGTGACGTCACATG)2.

Different methods for determining sugar conformations in large oligonucleotides have been evaluated using both J-coupling and NOE data. In order to stimulate COSY spectra, reliable estimates of line widths are required. We have measured T1p ( = T2) values for a large number of protons of the hexadecamer d(CATGTGACGTCACATG)2 using a new two-dimensional NMR experiment (T1RHOSY) to provide baseline information for the simulations. Both DQF-COSY and P.E.COSY cross-peaks have been systematically simulated as a function of line width, digitisation and signal-to-noise ratio. We find that for longer correlation times (tau > or = 5 ns), where line widths are comparable to or larger than active couplings, only sigma 1' (3J1'2'+3J1'2") is reasonably accurately determined (within +/- 1 Hz). Under these conditions, additional information is needed to determine the sugar conformation. We have used apparent distances H1'-H4' and H2"-H4', which provide a range of Ps over an interval of ca. 20 degrees. Complete analysis of time courses for intraresidue NOEs, with and without coupling constants, has also been evaluated for determining nucleotide conformations. Whereas Ps is poorly determined in the absence of both intrasugar NOEs and coupling constants, the range of solutions is decreased when intrasugar NOEs and sigma1' are also available. DQF-COSY, P.E.COSY and NOESY spectra at different mixing times of the hexadecamer d(CATGTGACGTCACATG)2 were recorded at three temperatures. A detailed analysis of the NOEs and coupling constants provided estimates of the sugar conformations in the hexadecamer. At 50 degrees C, the sugar conformations are well determined by the scalar and dipolar data, with pseudorotation phase angles of 126-162 degrees and mole fractions of the S conformation (fs) of 0.86 +/- 0.05. There was no statistically significant difference between fs for the purines and the pyrimidines, although there was a small tendency for Ps of the purines to be larger than those of the pyrimidines. At 25 degrees C, the sugar conformations were much less well determined, although the estimates of fs were the same within experimental error as at 50 degrees C. The experimental and theoretical results provide guidelines for the limits of conformational analysis of nucleic acids based on homonuclear NMR methods.

Base Sequence↗
PubMed1995

Interaction of minor-groove-binding diamidine ligands with an asymmetric DNA duplex. NMR and molecular modelling studies.

The aromatic diamidines berenil and propamidine bind reversibly to A+T-rich sites in the minor groove of B-form DNA duplexes. Based on extensive solution and crystallographic information we have designed a non-self-complementary double-stranded DNA sequence, d(GCAATGAGCG).d(CGCTCATTGC), that should contain a near-ideal binding site for berenil and a poorer site for the larger propamidine molecule, viz. d(AAT).d(ATT). 1H-NMR studies show that both ligands bind with 1:1 stoichiometry to the embedded 5'-AAT site, and induce numerous shifts of NMR resonances of DNA protons located in the minor groove. In addition, interactions with each strand can be distinguished by NOE spectroscopy due to the inherent asymmetry of the DNA. Detailed modelling based on experimental data show that no significant distortion of the B-DNA duplex is induced by either ligand. Sufficient NOE data were obtained to determine the position of the bound ligands in each complex. These conclusions are in agreement with predictions from molecular modelling calculations that provide a microscopic energy profile for interaction with the minor groove tract. Such calculations reveal an unexpected heterogeneous 5'-ATGA binding site that includes a spanned guanosine. This secondary binding site accounts for the extensive chemical shift perturbation induced by these ligands. The structures of the free DNA and the reversible complexes formed with each ligand molecule have been refined using an NOE-restrained isothermal annealing procedure. These structures confirm that the introduced ligands effect minimal perturbation of the helix, with binding to the 5'-AAT base sequence largely determined by specific non-bonded interactions.

Benzamidines↗
PubMed1995

Synthesis of two distamycin analogues and their binding mode to d(CGCAAATTTGCG)2 in the 2:1 solution complexes as determined by two-dimensional 1H-NMR.

In the course of a study aimed at the synthesis of pyrrole amidine carboxamide DNA-binding agents as novel pharmacological agents, a series of carbamoyl analogues of distamycin, containing an increasing number of pyrrole units, have been obtained by total synthesis. The interaction of the tetrapyrrole carbamoyl 4 with the dodecamer d(CGCAAATTTGCG)2 in comparison with that of the corresponding formylamino analogue 3 has been examined by high-resolution 1H-NMR and molecular modeling. Either ligand binds to DNA in one-drug and symmetric two-drug modes at low drug:DNA ratios, while at high ratios only the two-drug complex was observed. In this article, the structure of 2:1 drugs DNA complexes has been studied by NMR and molecular modeling, which indicate that the two analogues bind the DNA in a similar fashion, in the minor groove of the 5'-AATTT region. In both complexes the two drugs are symmetrically placed along the complementary strands of DNA with the pyrrole ring of one molecule in close contact with those of the other one. Although another region of five consecutive A-T base pairs is available, no evidence of sliding of drug molecules between different binding sites, as in the case of the 2:1 complex of distamycin with the same dodecamer, is observed, thus indicating that increasing the number of N-methylpyrrolecarboxamide units from three to four cases a lengthening of the recognition sequence.

Base Sequence↗
PubMed1995

Corrected transposition of the great arteries without associated defects in adult patients: clinical profile and follow up.

OBJECTIVE: To assess the clinical course of adult patients with corrected transposition of the great arteries without associated anomalies. DESIGN: All patients with corrected transposition of the great arteries without associated anomalies were reviewed with complete clinical and echocardiographic assessment. The complications were evaluated in each decade. SETTING: Tertiary centre with a specific unit dealing with "grown-up" adolescent and adult congenital heart disease, designated as a quaternary centre and a general hospital with a referral centre for "grown-up" congenital heart disease. PATIENTS: 18 patients (nine male and nine female) aged 16-61 years followed for 1-30 years (mean 10 years). RESULTS: There were no deaths. Six patients had a worsening ability index during follow up. Complications were: (a) complete heart block in seven, three of whom required pacemaker insertion; (b) significant left atrioventricular valve regurgitation in 50%, appearing only in the third decade (12%), with increasing frequency thereafter. Infective endocarditis was responsible for increasing left atrioventricular valve regurgitation in only one patient; (c) supraventricular arrhythmia appeared in the fifth decade, and occurred in all patients over the age of 60 years. One patient aged 61 had recurrent sustained ventricular tachycardia; and (d) congestive heart failure developed only after 50 years in 66%. One patient had severe left atrioventricular valve regurgitation; the function of the systemic ventricle was only moderately reduced in the other three. Three of the nine women had seven uneventful pregnancies. CONCLUSIONS: Patients with corrected transposition of the great arteries without associated defects may remain undiagnosed until adult life. Symptoms occur rarely before the fourth and fifth decades, when rhythm disturbance, left atrioventricular valve regurgitation, and moderately impaired systemic ventricular function cause congestive cardiac failure. The role of pacemaker insertion or surgery for left atrioventricular valve regurgitation needs further assessment.

Adolescent↗
PubMed1995

[Hypertrophic obstructive cardiomyopathy in a patient with Turner syndrome].

A case of hypertrophic obstructive cardiomyopathy in a patient with Turner syndrome is reported. The most frequently associated cardiac anomalies are coarctation of the aorta and bicuspid aortic valve. Hypertrophic cardiomyopathy has never been reported in this syndrome but is frequent in Noonan syndrome. In these two conditions the phenotype may be indistinguishable but the cariotype is different: normal in Noonan and 45X in Turner syndrome. Our patient had the typical somatic features, and the cariotype was 45X in all examined cells. A familial form of hypertrophic cardiomyopathy was excluded by the normal clinical examination of other members of the family. The presence of hypertrophic cardiomyopathy also in Turner syndrome and the recent localization on the long arm of the chromosome 12 of the gene for Noonan syndrome might postulate a common pathogenesis of the two syndromes.

Cardiomyopathy, Hypertrophic↗