Search PubMed⌕ Search

Biomedical subjects

A Aberg

Publications and source records attributed to A Aberg.

At least 37 records · Page 2Linked to original sources
PubMed1996

Crystallization and preliminary crystallographic analysis of the signal recognition particle SRPphi14-9 fusion protein.

The SRPphi14-9 fusion protein, which can functionally replace the SRP9/14 heterodimer in the mammalian signal recognition particle (SRP), has been crystallized using the vapor diffusion method. Four different crystal forms were grown. SRPphi14-9 form IV crystals belong to the space group P4(1)22/ P4(3)22 with cell parameters a = b = 69.7 Angstroms, c = 95.7 Angstroms, alpha = beta = gamma = 90 degrees. A complete data set to 2.8 Angstroms resolution with an Rsym on intensities of 7.0% was collected on a single flash-frozen crystal.

Amino Acid Sequence↗
PubMed1996

Crystallization and preliminary X-ray analysis of the 9 kDa protein of the mouse signal recognition particle and the selenomethionyl-SRP9.

Two different crystal forms of the 9 kDa protein of the signal recognition particle (SRP9) have been prepared by the hanging drop vapor diffusion technique using 28% (w/v) PEG8000 or 28% saturated ammonium sulphate as precipitant. The crystals are hexagonal bipyramids with average dimensions of 0.2 X 0.1 X 0.1 mm(3) and they diffract to a resolution of 2.3 Angstroms. They belong to the space groups P6(2)22/P6(4)22 or P3(1)21/P3(2)21 with cell dimensions a = b = 63.0 Angstroms, and c = 111.5 Angstroms. Crystals have also been grown from the selenomethionyl protein and multiwavelength data sets have been collected.

Animals↗
PubMed1996

Glucose levels and insulin secretion during a 75 g glucose challenge test in normal pregnancy.

OBJECTIVES: The aim of the study was to evaluate glucose levels and insulin secretion early in pregnancy and at a time when gestational diabetes mellitus frequently occurs in order to define reference values for glucose tolerance during pregnancy. The results were also related to maternal factors that might identify subjects at risk of developing gestational diabetes mellitus as well as foetal factors that might be a result of impaired glucose tolerance during pregnancy. DESIGN: A prospective study. SETTING: All Caucasian women attending one antenatal out-patient care unit were offered a 75 g oral glucose tolerance test at the 17th and 32nd week of gestation. SUBJECTS: A total of 586 consecutive pregnant women were included in the study. All 586 women were examined by repeated blood glucose measurements and 298 agreed to perform oral glucose tolerance tests as well. MAIN OUTCOME MEASURES: Venous whole blood glucose values were measured in the fasting state and in samples obtained 15, 30, 45, 60, 75, 90 and 120 min after oral intake of 75 g glucose. Serum insulin and C-peptide were also measured at these times. In all subjects, a random blood glucose sample was taken at the first visit, and thereafter at the 20th, 30th and 36th week of gestation. Information was also obtained from all subjects regarding body mass index, weight gain during pregnancy, smoking habits, family history of diabetes and hypertension, hypertension during pregnancy, past obstetric history, parity, and fetal outcome. RESULTS: The glucose tolerance was significantly impaired at the 32nd week of gestation compared with the 17th week of gestation. The mean +2SD 2 h glucose value during the oral glucose tolerance test at the 32nd week of gestation was 8.0 mmol L-1. Impaired glucose tolerance was characterised by increased insulin resistance, with a significant rise in serum insulin and C-peptide concentrations and in the insulin/glucose index during the oral glucose tolerance test at the 32nd week of gestation. Maternal factors associated with an impaired glucose tolerance were a family history of diabetes mellitus, smoking, a weight gain more than 18 kg during pregnancy, and glucosuria, while a family history of hypertension and hypertension present during pregnancy were not. Foetal factors that might be a result of impaired glucose tolerance during pregnancy, e.g. macrosomia and prematurity as well as complicated deliveries such as vacuum extraction/forceps or Caesarean section, all tended to be associated with higher blood glucose values. The same pattern was seen when the Apgar score was < 7. CONCLUSIONS: The results from this study show that the present cut-off values for diagnosis of gestational diabetes mellitus should be revised. Even if some maternal factors might indicate an increased risk for impaired glucose tolerance during pregnancy, they are probably not enough to detect women with gestational diabetes mellitus. Therefore, a screening programme for gestational diabetes should be considered.

Adult↗
PubMed1995

Crystallization of Thermus thermophilus histidyl-tRNA synthetase and its complex with tRNAHis.

Histidyl-tRNA synthetase (HisRS) has been purified from the extreme thermophile Thermus thermophilus. The protein has been crystallized separately with histidine and with its cognate tRNAHis. Both crystals have been obtained using the vapor diffusion method with ammonium sulphate as precipitant. The crystals of HisRS with histidine belong to the spacegroup P2(1)2(1)2 with cell parameters a = 171.3 A, b = 214.7 A, c = 49.3 A, alpha = beta = gamma = 90 degrees. A complete data set to a resolution of 2.7A with an Rmerge on intensities of 4.1% has been collected on a single frozen crystal. A partial data set collected on a crystal of HisRS in complex with tRNAHis shows that the crystals are tetragonal with cell parameters a = b = 232 A, c = 559 A, alpha = beta = gamma = 90 degrees and diffract to about 4.5 A resolution.

Crystallography, X-Ray↗
PubMed1995

A new symphysis-fundus height growth chart based on a well defined female population with ultrasound-dated singleton pregnancies.

BACKGROUND: The aim was to construct a new symphysis-fundus (SF) height growth chart, based on ultrasound-dated singleton pregnancies. METHODS: We made a population-based study of all women, from the catchment areas of three district antenatal clinics, who registered for antenatal care during 1986. The growth of the SF height was measured on 403 women with singleton pregnancies. RESULTS: During pregnancy each woman made on average 14.0 (s.d. 2.8) visits to the antenatal clinic, where the SF height was measured on average 10.4 (s.d. 2.6) times. All but two women had an ultrasound examination. Using proper longitudinal methods a new SF height growth chart was constructed. CONCLUSION: The mean values of the present curve, based on longitudinal data, were almost identical with the mean values of a recently presented curve based on stratified cross-sectional data. Both these Swedish studies were population-based and the pregnancies were ultrasound-dated.

Adult↗
PubMed1995

[Princess Eugénie and her work for the benefit of disabled children].

Princess Eugénie was the daughter of the Swedish-Norwegian king Oscar I. She had a very good education; her favourite subjects were art and music. In the Spring of 1852, when she was 22 years old, she was stricken with a severe disease, and she was paralysed in one leg. During her illness she underwent a religious crisis. After recovering, her main interest was to assist poor and incurably ill children. Her name is above all associated with the Home of Eugénie (Eugenia-hemmet) in Stockholm, which was opened in 1886. This home accommodated at this time 45 children, but very soon the number increased. According to the regulations, the Home of Eugénie was to become a real home for these children. They were allowed to stay there until the age of 15, and to get a complete medical attention. They were also to receive an education as well as a vocational training. The princess put down most of her interest and her energy in the home. She knew all the children, started fundraising in aid for them. She herself donated them all her earnings. She even made porcelaine figurines which were spread and sold in big numbers. She died in 1889.

Adolescent↗
PubMed1994

Effects of felodipine versus nifedipine on exercise tolerance in stable angina pectoris.

The effects of single doses of felodipine (5 and 10 mg) and nifedipine (10 and 20 mg) on chronic stable effort angina pectoris were assessed in a placebo-controlled, double-blind, crossover study of 24 patients receiving beta blockers and short-acting nitroglycerin. The effects were measured by repeated bicycle ergometer tests. The total work, and time until 1 mm of ST depression increased significantly by 9 to 31% after both active drugs at both dose levels in comparison with placebo. The differences were not significant between drugs or doses. At rest, blood pressure decreased (10 to 15%) and heart rate increased (5 to 10%) significantly after both active drugs. During exercise at the highest comparable work load, systolic blood pressure decreased significantly (23 to 26%), whereas heart rate was not affected after felodipine and nifedipine compared with placebo. The 2 drugs were well tolerated, and side effects were mild. Therefore, single doses of 5 and 10 mg of felodipine, and 10 and 20 mg of nifedipine have similar antianginal and anti-ischemic properties. However, felodipine has a longer duration of action, which may improve compliance.

Analysis of Variance↗
PubMed1994

The conserved serine 211 is essential for reduction of the dinuclear iron center in protein R2 of Escherichia coli ribonucleotide reductase.

The R2 protein family of class I ribonucleotide reductases contains a highly conserved serine residue close to the essential tyrosyl radical and the dinuclear iron center. In order to test its physiological importance, we have engineered the Ser-211 of Escherichia coli R2 to an alanine and a cysteine residue. The three-dimensional structure of R2 S211A solved to 2.4-A resolution is virtually identical to the wild-type structure apart from the substituted residue. Both mutant proteins contain oxidized dinuclear iron and tyrosyl radical, and their specific enzyme activity per radical are comparable to that of the wild-type protein. In R2 S211A the stability of the tyrosyl radical is substantially decreased, probably caused by movement of Gln-80 into hydrogen bonding distance of Tyr-122. The major defect in R2 S211A, however, is the inability of its iron center to be reduced by enzymic or chemical means, a characteristic not found in R2 S211C. We propose that Ser-211 is needed as a proton donor/transporter during reduction of the iron center of R2, a reaction which in vivo precedes reconstitution of the tyrosyl radical. This offers a physiological explanation for the high conservation of a serine residue at this position in the R2 family.

Amino Acid Sequence↗
PubMed1993

Autocatalytic generation of dopa in the engineered protein R2 F208Y from Escherichia coli ribonucleotide reductase and crystal structure of the dopa-208 protein.

The mutant form Phe-208-->Tyr of the R2 protein of Escherichia coli ribonucleotide reductase contains an intrinsic ferric-Dopa cofactor with characteristic absorption bands at 460 and ca. 700 nm [Ormö, M., de Maré, F., Regnström, K., Aberg, A., Sahlin, M., Ling, J., Loehr, T. M., Sanders-Loehr, J., & Sjöberg, B. M. (1992) J. Biol. Chem. 267, 8711-8714]. The three-dimensional structure of the mutant protein, solved to 2.5-A resolution, shows that the Dopa is localized to residue 208 and that it is a bidentate ligand of Fe1 of the binuclear iron center of protein R2. Nascent apoR2 F208Y, lacking metal ions, can be purified from overproducing cells grown in iron-depleted medium. ApoR2 F208Y is rapidly and quantitatively converted to the Dopa-208 form in vitro by addition of ferrous iron in the presence of oxygen. Other metal ions (Cu2+, Mn2+, Co2+) known to bind to the metal site of wild-type apoR2 do not generate a Dopa in apoR2 F208Y. The autocatalytic generation of Dopa does not require the presence of a tyrosine residue at position 122, the tyrosine which in a wild-type R2 protein acquires the catalytically essential tyrosyl radical. It is proposed that generation of Dopa initially follows the suggested reaction mechanism for tyrosyl radical generation in the wild-type protein and involves a ferryl intermediate, which in the case of the mutant R2 protein oxygenates Tyr 208. This autocatalytic metal-mediated reaction in the engineered R2 F208Y protein may serve as a model for formation of covalently bound quinones in other proteins.

Apoproteins↗
PubMed1993

Unusual clustering of carboxyl side chains in the core of iron-free ribonucleotide reductase.

The principal driving forces of protein folding are the burial of hydrophobic residues in the interior of proteins and the exposure of charged residues at the surface. Charged residues are only occasionally found in the interior, where they form hydrogen bonds to oppositely charged residues or main-chain atoms. Ribonucleotide reductase, a key enzyme in DNA synthesis, catalyses the de novo production of deoxyribonucleotide precursors. It is composed of two different dimeric proteins R1 and R2 (refs 3-5). R2 subunits contain buried iron-centres with each centre formed by two ferric ions coordinated by four carboxylates and two histidine ligands. Iron-free R2, apoR2, is a precursor of active R2 and folds into a stable protein which is transformed into active R2 by ferrous ions and molecular oxygen. Here we show that the iron-free protein does not undergo any major structural changes compared with the iron-containing R2. The effect of this is a clustering of four carboxyl side chains in the interior of the subunit, in contrast to the normal distribution of charged residues in proteins.

Amino Acid Sequence↗
PubMed1992

Substitution of manganese for iron in ribonucleotide reductase from Escherichia coli. Spectroscopic and crystallographic characterization.

Each polypeptide chain of protein R2, the small subunit of ribonucleotide reductase from Escherichia coli, contains a stable tyrosyl radical and two antiferromagnetically coupled oxo-bridged ferric ions. A refined structure of R2 has been recently obtained. R2 can be converted into apoR2 by chelating out the metal cofactor and scavenging the radical. This study shows that apoR2 has a very strong affinity for four stable Mn2+ ions. The manganese-containing form of R2, named Mn-R2, has been studied by EPR spectroscopy and x-ray crystallography. It contains two binuclear manganese clusters in which the two manganese ions occupy the natural iron-binding sites and are only bridged by carboxylates from glutamates 115 and 238. This in turn explains why the spin-exchange interaction between the two ions is very weak and why Mn-R2 is EPR active. Mn-R2 could provide a model for the native diferrous form of protein R2, and a detailed molecular mechanism for the reduction of the iron center of protein R2 is proposed.

Amino Acid Sequence↗
PubMed1992

Engineering of the iron site in ribonucleotide reductase to a self-hydroxylating monooxygenase.

Protein R2 of ribonucleotide reductase contains a dinuclear ferric iron center adjacent to a tyrosyl radical in the interior of the protein matrix. A patch of hydrophobic residues surrounds the iron-radical cofactor. Its importance during the oxidative generation of the iron-radical cofactor was investigated by site-directed mutagenesis of Phe-208 to tyrosine. The mutant protein R2 F208Y has prominent absorption bands at 460 and 720 nm reminiscent of those in ferric-catecholate complexes. Resonance Raman spectroscopy shows that the iron center of R2 F208Y contains a bidentate catechol ligand. The mechanism for generation of this protein-derived dihydroxyphenylalanine may be similar to the catalytic cycle of methane monooxygenase.

Base Sequence↗
PubMed1992

Competence and compliance in antenatal care. Experience from Sweden.

Swedish antenatal care is staffed by midwives working within the primary health care system, but with close collaboration with the hospital. The compliance to the program both from staff and mothers is very high, with 13.2 visits on average. There is a regional variation both in the number of visits and in the use of routine tests.

Female↗