Molecular basis for recognition and deubiquitination of 40S ribosomes by Otu2.

In actively translating 80S ribosomes the ribosomal protein eS7 of the 40S subunit is monoubiquitinated by the E3 ligase Not4 and deubiquitinated by Otu2 upon ribosomal subunit recycling. Despite its importance for translation efficiency the exact role and structural basis for this translational reset is poorly understood. Here, structural analysis by cryo-electron microscopy of native and reconstituted Otu2-bound ribosomal complexes reveals that Otu2 engages 40S subunits mainly between ribosome recycling and initiation stages.

Disordered region of H3K9 methyltransferase Clr4 binds the nucleosome and contributes to its activity.

Heterochromatin is a distinctive chromatin structure that is essential for chromosome segregation, genome stability and regulation of gene expression. H3K9 methylation (H3K9me), a hallmark of heterochromatin, is deposited by the Su(var)3-9 family of proteins; however, the mechanism by which H3K9 methyltransferases bind and methylate the nucleosome is poorly understood. In this work we determined the interaction of Clr4, the fission yeast H3K9 methyltransferase, with nucleosomes using nuclear magnetic resonance, biochemical and genetic assays.

Fuzzy Interactions Form and Shape the Histone Transport Complex.

Protein transport into the nucleus is mediated by transport receptors. Import of highly charged proteins, such as histone H1 and ribosomal proteins, requires a dimer of two transport receptors. In this study, we determined the cryo-EM structure of the Imp7:Impβ:H1.

Preparative two-step purification of recombinant H1.0 linker histone and its domains.

H1 linker histones are small basic proteins that have a key role in the formation and maintenance of higher-order chromatin structures. Additionally, many examples have shown that linker histones play an important role in gene regulation, modulated by their various subtypes and posttranslational modifications. Obtaining high amounts of very pure linker histones, especially for efficient antibody production, remains a demanding and challenging procedure.

Adaptation of aminoacyl-tRNA synthetase catalytic core to carrier protein aminoacylation.

Amino acid:[carrier protein] ligases (aa:CP ligases) are recently discovered enzymes that are highly similar to class II aminoacyl-tRNA synthetases (aaRSs). However, while aaRSs aminoacylate tRNA and supply building blocks for ribosomal translation, aa:CP ligases transfer activated amino acids to the phosphopantetheine group of small carrier proteins. We have solved the crystal structure of an aa:CP ligase complexed with the carrier protein (CP).

Structure-function relationships of two paralogous single-stranded DNA-binding proteins from Streptomyces coelicolor: implication of SsbB in chromosome segregation during sporulation.

The linear chromosome of Streptomyces coelicolor contains two paralogous ssb genes, ssbA and ssbB. Following mutational analysis, we concluded that ssbA is essential, whereas ssbB plays a key role in chromosome segregation during sporulation. In the ssbB mutant, ∼30% of spores lacked DNA.

Probing enzyme promiscuity of SGNH hydrolases.

Several hydrolases of the SGNH superfamily, including the lipase SrLip from Streptomyces rimosus (Q93MW7), the acyl-CoA thioesterase I TesA from Pseudomonas aeruginosa (Q9HZY8) and the two lipolytic enzymes EstA (from P. aeruginosa, O33407) and EstP (from Pseudomonas putida, Q88QS0), were examined for promiscuity. These enzymes were tested against four chemically different classes of a total of 34 substrates known to be hydrolysed by esterases, thioesterases, lipases, phospholipases, Tweenases and proteases.

Homologs of aminoacyl-tRNA synthetases acylate carrier proteins and provide a link between ribosomal and nonribosomal peptide synthesis.

Aminoacyl-tRNA synthetases (aaRSs) are ancient and evolutionary conserved enzymes catalyzing the formation of aminoacyl-tRNAs, that are used as substrates for ribosomal protein biosynthesis. In addition to full length aaRS genes, genomes of many organisms are sprinkled with truncated genes encoding single-domain aaRS-like proteins, which often have relinquished their canonical role in genetic code translation. We have identified the genes for putative seryl-tRNA synthetase homologs widespread in bacterial genomes and characterized three of them biochemically and structurally.

Idiosyncratic helix-turn-helix motif in Methanosarcina barkeri seryl-tRNA synthetase has a critical architectural role.

All seryl-tRNA synthetases (SerRSs) are functional homodimers with a C-terminal active site domain typical for class II aminoacyl-tRNA synthetases and an N-terminal domain involved in tRNA binding. The recently solved three-dimensional structure of Methanosarcina barkeri SerRS revealed the idiosyncratic features of methanogenic-type SerRSs; that is, an active site zinc ion, a unique tRNA binding domain, and an insertion of approximately 30 residues in the catalytic domain, which adopt a helix-turn-helix (HTH) fold. Here, we present biochemical evidence for multiple roles of the HTH motif; it is important for dimerization of the enzyme, contributes to the overall stability, and is critical for the proper positioning of the tRNA binding domain relative to the catalytic domain.

Cardiac autonomic nervous system in patients with myotonic dystrophy type 1.

The purpose of the present study was to evaluate cardiac autonomic nervous system (ANS) in patients with myotonic dystrophy type 1 (DM1). The function of ANS was studied in 20 patients with DM1 and 15 healthy controls. All subjects were investigated by a battery of six cardiovascular autonomic tests and power spectral analysis of heart rate variability (HRV).

The coronary subclavian steal syndrome: an uncommon sequel to internal mammary-coronary artery bypass surgery.

Coronary subclavian steal syndrome is a possible sequel in patients who have undergone myocardial revascularization with an internal mammary artery. We report a case of this syndrome in a 67-years-old man. In 1990 he underwent a quadruple bypass: aorta-obtuse margin, aorta-right coronary (two sequential), internal artery mammary-descending coronary artery.

Chylothorax after pleuro-pulmonary surgery: a rare but unavoidable complication.

The incidence of chylothorax after pleuro-pulmonary operations as well as its treatment is reported. Of 1744 operations performed postoperative chylothorax developed in 13 (0.74%).

Lung resections concomitant to coronary artery bypass grafting.

From 1980 through 1993 ten patients underwent concomitant coronary artery bypass grafting and lung resection via median sternotomy. In eight patients a lung malignancy was resected, of which one was a small cell lung cancer. The lung resection was carried out before cardiopulmonary bypass in eight patients and during cardiopulmonary bypass in two.

[The aneurysmal degeneration of aortocoronary bypasses. A case report].

A 67-year-old man presenting with oppressive atypical chest pain 13 years after aorto-coronary saphenous vein bypass surgery, was found to have a large left anterior mediastinal mass on chest x-rays. Computerized tomography and digital subtraction angiography showed conflicting evidence on the vascular nature of the structure: the suspect diagnosis was of aortic pseudoaneurysm originating in the area of previous aortic cannulation. Selective coronary and bypass angiography showed extreme irregularity and dilatation of the grafts, and revealed the mediastinal mass to be represented by aneurysmal dilatation of the saphenous vein graft to the obtuse marginal coronary artery, partially filled with thrombus.

[Lipoma of the interventricular septum: its diagnosis and treatment].

We describe a case of left ventricular intramyocardial lipoma in a patient symptomatic for chest pain and syncope. The two-dimensional echocardiographic investigation showed a hyperechogenic mass inside the interventricular septum; presence of the mass was confirmed by CT scan and nuclear magnetic resonance imaging. In our experience only the CT scan was useful to clearly identify the histologic characteristics of tissue.

[Two-dimensional echocardiographic diagnosis of a thromboembolic mass in the right atrium].

We describe the case of a patient with massive pulmonary embolism, in which two-dimensional echocardiography demonstrated the presence of a free-floating mass in the right atrial cavity. The patient was urgently and successfully operated on. We describe the echocardiographic findings and emphasize the value of two dimensional echocardiography in detecting right-sided intracavitary thromboemboli, a condition in which immediate surgical treatment is mandatory.

[Interatrial defect functionally cancelled by a left atrial myxoma within the framework of embolizing mitral stenosis and insufficiency].

The case is presented by a 54 year-old woman, studied because of a clinical diagnosis of mitral valve disease, in which echocardiographic and angiocardiographic examination afforded the diagnosis of left atrial tumor. The surgical finding was of a large myxoma implanted on the atrial septum and prolapsing into the mitral opening and engaging with a branch into an atrial septal defect of the cavalis superior type. Some considerations are made on the times of possible origin and growth of the tumor; the complete absence of the increased pulmonary flow in the presence of a large interatrial communication suggested an early beginning of the tumor that, obstructing the defect, might have hindered the hemodynamic derangement.

[Surgical treatment of postinfarctual left ventricular aneurysm (author's transl)].

Ventricular aneurysm is a frequent complication of myocardial infarction, but its diagnostic and prognostic implications are not fully defined. A surgical series of 66 ventricular resections for symptomatic left ventricular aneurysm is analyzed. Pts.

[Surgical complications of pacemaker implantation (author's transl)].

During the period 1966-1977, 705 pacemaker implantations with transvenous endocardial electrode and 369 substitutions of generators were carried out, besides 275 operations treating some complications after implantation were required. The most frequent complications were: endocardial electrode dislocation (9.4%), lesion caused by decubitus (7.