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Biomedical subjects

M Saraste

Publications and source records attributed to M Saraste.

At least 91 records · Page 5Linked to original sources
PubMed1994

Structure and evolution of cytochrome oxidase.

The structural features of cytochrome oxidases are reviewed in light of their evolution. The substrate specificity (quinol vs. cytochrome c) is reflected in the presence of a unique copper centre (CuA) in cytochrome c oxidases. In several lines of evolution, quinol oxidases have independently lost this copper. Also, the most primitive cytochrome c oxidases do not contain this copper, and electron entry takes place via c-type haems. These enzymes, exemplified by the rhizobial FixN complex, probably remind the first oxidases. They are related to the denitrification enzyme nitric oxide reductase.

Bacteria↗
PubMed1994

Myocardial viability: fluorine-18-deoxyglucose positron emission tomography in prediction of wall motion recovery after revascularization.

To assess the value of positron emission tomography (PET) imaging with fluorine-18-deoxyglucose ([18F]FDG) in predicting cardiac wall motion recovery after revascularization, 48 consecutive patients with previous myocardial infarction were studied. The normalized [18F]FDG uptake at rest was assessed semiquantitatively and compared to perfusion at rest as studied by SPECT imaging. Wall motion was analyzed with echocardiography before and after revascularization. Wall motion recovery occurred in 27 (30%) of the revascularized 90 dysfunctional segments. Preserved [18F]FDG uptake (mean +/- 2 SD) was commonly found in dysfunctional segments, but only 54% of these segments recovered after revascularization. Subnormal [18F]FDG uptake identified accurately the segments with no potential to recover (predictive value 100%). By using an optimized threshold value for normalized [18F]FDG uptake, the sensitivity of 85% and specificity of 84% to predict functional recovery were reached simultaneously. However, in the segments with moderately or severely reduced perfusion at rest, the diagnostic accuracy of [18F]FDG uptake for viability was 100%. The results of this study show that the presence of viable tissue indicated by preserved [18F]FDG uptake does not inevitably imply functional recovery after revascularization. However, acceptable diagnostic accuracy for viability might be reached by [18F]FDG alone, providing that appropriate uptake limits are used. The combined evaluation of [18F]FDG uptake and perfusion enables precise assessment of myocardial viability.

Angioplasty, Balloon, Coronary↗
PubMed1994

High-resolution crystal structures of tyrosine kinase SH3 domains complexed with proline-rich peptides.

Src-homology 3 (SH3) domains bind to proline-rich motifs in target proteins. We have determined high-resolution crystal structures of the complexes between the SH3 domains of Abl and Fyn tyrosine kinases, and two ten-residue proline-rich peptides derived from the SH3-binding proteins 3BP-1 and 3BP-2. The X-ray data show that the basic mode of binding of both proline-rich peptides is the same. Peptides are bound over their entire length and interact with three major sites on the SH3 molecules by both hydrogen-bonding and van der Waals contacts. Residues 4-10 of the peptide adopt the conformation of a left-handed polyproline helix type II. Binding of the proline at position 2 requires a kink at the non-proline position 3.

Amino Acid Sequence↗
PubMed1994

The purified SoxABCD quinol oxidase complex of Sulfolobus acidocaldarius contains a novel haem.

A respiratory quinol oxidase complex that is encoded by the soxABCD operon has been purified from the thermoacidophilic archaeon Sulfolobus acidocaldarius. The enzyme was solubilized with dodecyl maltoside and purified in the presence of this detergent and ethylene glycol. The complex is hydrodynamically homogeneous and contains at least five different polypeptides. In addition to the major subunits SoxA, SoxB and SoxC, it has two small polypeptides. One of these is the translation product of a short open reading frame (now called the soxD gene) at the end of the operon. The optical and electron paramagnetic resonance spectra of the SoxABCD complex have been characterized. It probably contains four A-type haems which are bound to SoxB and SoxC. The structure of these haems is not identical to haem A. The novel haem As has a 2-hydroxyethyl geranylgeranyl in position 2 of the porphyrin ring whereas haem A has the related farnesyl-containing side-chain.

Bacterial Proteins↗
PubMed1994

Doppler-derived systolic pulmonary artery pressure in acute neonatal respiratory distress syndrome.

OBJECTIVE: To determine the course of systolic pulmonary artery pressure (PAP) in association with ductal shunting and cardiac output (CO) in preterm neonates. DESIGN: During the acute phase of respiratory distress syndrome (RDS) with and without surfactant treatment, serial Doppler ultrasound examinations were performed at the ages of 2, 12, 24, 48, and 72 hours in 51 neonates with RDS and 21 healthy, preterm controls. Twenty-eight of the distressed neonates received two or four doses of synthetic exogenous surfactant at intervals of 12 hours. Measurements of hemodynamic variables in these neonates were performed before and after 8 hours following surfactant treatments. PAP was estimated by the Doppler method from the maximal tricuspid regurgitant flow velocity. Doppler ultrasound was also used to determine simultaneously CO, and the direction and magnitude of the ductal shunting. RESULTS: The PAP was initially at the same level, but remained significantly higher in distressed than in healthy, preterm control neonates between the ages of 12 to 48 hours. The systolic systemic arterial blood pressures did not differ between the distressed and control neonates, but increased gradually during the study period. Consequently, the ratio of systolic pulmonary and systemic pressure was also higher in neonates with RDS than in controls during the first day of life. Bidirectional ductal shunting disappeared in all neonates studied after 2 days of life. Significant left-to-right shunting through the ductus arteriosus persisted more frequently in distressed neonates, especially those with surfactant treatment, than in control neonates during the study period, and more often caused the need for medical or surgical closure. Doppler-derived CO remained stable throughout the study in the distressed neonates, being significantly higher in surfactant-treated neonates than nontreated distressed neonates or healthy controls at 72 hours of life. CONCLUSIONS: The data of the present study confirms that the postnatal decrease in PAP is delayed in acute RDS. Further, significant patent ductus arteriosus shunting persists longer in RDS and may contribute to elevated CO during the resolution of the disease.

Acute Disease↗
PubMed1993

Soluble CuA-binding domain from the Paracoccus cytochrome c oxidase.

In cytochrome c oxidase the C-terminal part of subunit II is outside the membrane and contains a copper center called CuA. We have expressed this domain of the Paracoccus denitrificans oxidase in a soluble form. Data obtained by quantitative copper-to-protein measurements, electrospray mass spectrometry, and electron paramagnetic resonance spectroscopy show that the center contains two copper atoms probably in a mixed valence configuration. Its absorbance spectrum is similar to that of the copper center A in nitrous oxide reductase. The EPR spectrum suggests that the center in the soluble protein is closely related to the native CuA site in the cytochrome oxidase complex. However, it seems likely that the copper center in the soluble domain is more exposed to the aqueous milieu than in the intact complex because its absorbance and EPR spectra are sensitive to pH. At alkaline pH one of the coppers in the site acquires type-2 character, indicating that it may be coordinated to a new ligand. The pK of this reversible change is about 8.2. The CuA-binding fragment is able to oxidize cytochrome c.

Amino Acid Sequence↗
PubMed1993

F1F0-ATP synthase from bovine heart mitochondria: development of the purification of a monodisperse oligomycin-sensitive ATPase.

A new procedure for the isolation of ATP synthase from bovine mitochondria has been developed, with the primary objective of producing enzyme suitable for crystallization trials. Proteins were extracted from mitochondrial membranes with dodecyl-beta-D-maltoside, and the ATP synthase was purified from the extract in the presence of the same detergent by a combination of ion-exchange and gel-filtration chromatography and ammonium sulphate precipitation. This simple and rapid procedure yields 20-30 mg of highly pure and monodisperse enzyme, evidently consisting of 14 different subunits, amongst them, in apparently stoichiometric amounts with the established subunits, subunit e, a recently discovered subunit of unknown function. The enzyme preparation has an oligomycin-sensitive ATP hydrolysis activity, and so the F1 domain is functionally associated with the membrane domain, F0. In contrast with the N-termini of some of the subunits of bovine mitochondrial F1-ATPase, those of the F1F0-ATP synthase are not degraded by proteolysis during the isolation procedure. This preparation therefore satisfies prerequisites for crystallization trials.

Adenosine Triphosphate↗
PubMed1993

Two cysteines, two histidines, and one methionine are ligands of a binuclear purple copper center.

Cytochrome c oxidase contains a copper center, CuA, which is involved in electron transfer from cytochrome c to the oxygen-reducing active site. This center is distinct from types 1, 2, and 3 copper sites and related only to a purple copper center in nitrous oxide reductase. At present it is not clear whether this site is mononuclear or is comprised of two copper atoms in a mixed valence (Cu(I)-Cu(II)) configuration. Here we use a model of CuA, engineered into a structurally related but initially copperless protein, to study the structure of this copper center. The results from biochemical analysis, site-directed mutagenesis, and electrospray mass spectrometry support the binuclear model. Two cysteines, two histidines, and one methionine are the major ligands of two coppers. Substitution of these residues results in either a complete loss of color or dramatic changes in the absorbance spectrum. In contrast, substitution of the invariant glutamate residue, which is located between the copper-binding cysteines, leads to a minor perturbation of the optical spectrum.

Amino Acid Sequence↗
PubMed1993

Crystallization and preliminary X-ray analysis of the periplasmic fragment of CyoA-a subunit of the Escherichia coli cytochrome o complex.

CyoA, an integral membrane protein, is a subunit of the Escherichia coli cytochrome o quinol oxidase complex. The C-terminal periplasmic domain of CyoA has been expressed in E. coli, purified and crystallized. Crystals were grown using ammonium sulphate as a precipitant. They have space group I222 or I2(1)2(1)2(1) and diffract X-rays to 2.3 A resolution.

Crystallization↗
PubMed1993

The PH domain: a common piece in the structural patchwork of signalling proteins.

The 'pleckstrin homology' domain is an approximately 100-residue protein module that has recently been added to the domain catalogue of signalling proteins. For this review we have made an extensive database search using a profile search method, and found a number of additional proteins that may contain PH domains. The PH domain is present in many kinases, isoforms of phospholipase C, GTPases, GTPase-activating proteins and nucleotide-exchange factors, including such proteins as Vav, Dbl and Bcr, and there are two PH domains in a guanine-nucleotide releasing factor of Ras. Many PH-domain-containing proteins interact with GTP-binding proteins. We have also identified a PH domain in beta-adrenergic receptor kinase exactly in the region that has already been shown to be involved in binding to the beta and gamma subunits of a heterotrimeric G protein. This suggests that PH domains may be involved in interactions with GTP-binding proteins.

Amino Acid Sequence↗
PubMed1993

Pulmonary hemodynamics after synthetic surfactant replacement in neonatal respiratory distress syndrome.

To evaluate the acute effects of surfactant replacement therapy on pulmonary circulation in neonatal respiratory distress syndrome, we studied 25 infants before and for 1 hour after either synthetic surfactant administration (n = 15) or endotracheal suctioning (n = 10). The noninvasive Doppler method was used to estimate systolic pulmonary artery pressure from tricuspid regurgitant flow velocity and to measure blood flow velocity of the left-to-right shunt through the ductus arteriosus. Pulmonary artery pressure decreased significantly within 15 minutes after surfactant administration and remained low throughout the study period, whereas suctioning did not change pulmonary artery pressure levels. No changes in systemic pressure were found in either group. Velocity of the ductal left-to-right shunting increased and remained elevated for 1 hour only in surfactant-treated infants. In addition, right-to-left ductal shunting disappeared in four infants after surfactant administration. Our data thus indicate that administration of synthetic surfactant to infants with respiratory distress syndrome reduces pulmonary vascular resistance, resulting in a decrease in pulmonary artery pressure and an increase in ductal flow velocity.

Blood Flow Velocity↗
PubMed1993

Crystal structure of the SH3 domain in human Fyn; comparison of the three-dimensional structures of SH3 domains in tyrosine kinases and spectrin.

The Src-homology 3 (SH3) region is a protein domain consisting of approximately 60 residues. It occurs in a large number of eukaryotic proteins involved in signal transduction, cell polarization and membrane--cytoskeleton interactions. The function is unknown, but it is probably involved in specific protein--protein interactions. Here we report the crystal structure of the SH3 domain of Fyn (a Src family tyrosine kinase) at 1.9 A resolution. The crystals have two SH3 molecules per asymmetric unit. These two Fyn SH3 domains are not related by a local twofold axis. The crystal structures of spectrin and Fyn SH3 domains as well as the solution structure of the Src SH3 domain show that these all have the same basic fold. A protein domain which has the same topology as SH3 is present in the prokaryotic regulatory enzyme BirA. The comparison between the crystal structures of Fyn and spectrin SH3 domains shows that a conserved surface patch, consisting mainly of aromatic residues, is flanked by two hairpin-like loops (residues 94-104 and 114-118 in Fyn). These loops are different in tyrosine kinase and spectrin SH3 domains. They could modulate the binding properties of the aromatic surface.

Bacterial Proteins↗
PubMed1993

The value of quantitative analysis of glucose utilization in detection of myocardial viability by PET.

To study whether absolute quantitation of regional myocardial glucose utilization (rMGU) enhances detection of myocardial viability, 70 nondiabetic patients with prior myocardial infarction and angiographically confirmed coronary artery disease were studied with [18F]FDG PET after oral glucose loading. Forty-eight patients were also revascularized and underwent echocardiography after revascularization to detect wall motion recovery. The rMGU was calculated in eight myocardial segments in each patient and the results were compared to normalized (relative) [18F]FDG uptake values. In normal segments (n = 225), rMGU was 56 +/- 18 mumole/min/100 g (mean +/- s.d.) and relative [18F]FDG uptake 97% +/- 12%. The interindividual variation of rMGU in normal myocardium was greater than the intraindividual variation (s.d. 31% versus 11%). The respective values for relative [18F]FDG uptake were 9% and 10%. Both rMGU and [18F]FDG uptake were significantly reduced in segments with scarring observed visually during bypass surgery (29 +/- 19 mumole/min/100 g and 45% +/- 22%, n = 26). The rMGU and [18F]FDG uptake were higher in segments that recovered after revascularization (53 +/- 17 mumole/min/100/g and 110% +/- 21%, n = 27) than in those that did not (37 +/- 20 mumole/min/100 g and 65% +/- 24%, n = 63). However, due to larger variability of rMGU values, normalized [18F]FDG uptake was superior to rMGU in separating normal and scar segments as well as in predicting wall motion recovery. We conclude that rMGU variability is notable and is caused mainly by variations between patients. Interindividual variation is reduced by normalization, which results in more accurate assessment of myocardial viability. Thus, static imaging and semiquantitative analysis are sufficient for the clinical assessment of myocardial viability.

Coronary Angiography↗
PubMed1992

Crystal structure of a Src-homology 3 (SH3) domain.

The Src-homologous SH3 domain is a small domain present in a large number of proteins that are involved in signal transduction, such as the Src protein tyrosine kinase, or in membrane-cytoskeleton interactions, but the function of SH3 is still unknown (reviewed in refs 1-3). Here we report the three-dimensional structure at 1.8 A resolution of the SH3 domain of the cytoskeletal protein spectrin expressed in Escherichia coli. The domain is a compact beta-barrel made of five antiparallel beta-strands. The amino acids that are conserved in the SH3 sequences are located close to each other on one side of the molecule. This surface is rich in aromatic and carboxylic amino acids, and is distal to the region of the molecule where the N and C termini reside and where SH3 inserts into the alpha-spectrin chain. We suggest that a protein ligand binds to this conserved surface of SH3.

Amino Acid Sequence↗
PubMed1992

SH3--an abundant protein domain in search of a function.

Src-homology 3 is a small protein domain of about 60 amino acid residues. It is probably made of beta-sheets. SH3 is present in a large number of eukaryotic proteins which are involved in signal transduction, cell polarization and membrane-cytoskeleton interactions. Here we review its occurrence and discuss possible functions of this domain.

Amino Acid Sequence↗