Pulmonary arterial hypertension in a patient with stage II sarcoidosis and Hashitoxicosis.

Although pulmonary arterial hypertension is usually associated with advanced stages of sarcoidosis, its occurrence in early stage disease is rare. Herein, a case of associated pulmonary arterial hypertension in the setting of Hashitoxicosis and stage II pulmonary sarcoidosis is reported. The case of associated pulmonary arterial hypertension occurred in a young female without clinically significant medical history and who completely recovered after receiving oral corticotherapy only. Furthermore, this case report suggests the presence of an interaction between pulmonary arterial hypertension, sarcoidosis and Hashitoxicosis.

Spontaneous rupture of a Dacron prosthesis.

This case report concerns a spontaneous rupture of a Dacron prosthesis 19 years after its insertion. The rupture occurRed in the mid-graft portion, remote from the anastomoses and was not associated with proved infection. It was the result of an intrinsic deterioration of the graft textile structure. The patient recovered after insertion of a new Dacron graft. The authors discuss the incidence of graft degeneration and the causative factors. Lesions on the frame of the graft could be due to a variety of factors such as intrinsic Dacron graft factors, manufacturing, inappropriate utilization, physical, enzymatic or immunological factors.

Novel concepts for selection of catalytic activity.

The selection of mutant enzymes with novel properties from libraries is emerging as a very powerful strategy for enzyme engineering. The past year has witnessed significant progress on several fronts: new and improved methods have been developed for the creation of libraries and advances have been made in screening and selection techniques. The results achieved demonstrate the enormous potential of the methods and leave questions open for further studies.

CENTA as a chromogenic substrate for studying beta-lactamases.

CENTA, a chromogenic cephalosporin, is readily hydrolyzed by beta-lactamases of all classes except for the Aeromonas hydrophila metalloenzyme. Although it cannot practically be used for the detection of beta-lactamase-producing strains on agar plates, it should be quite useful for kinetic studies and the detection of the enzymes in crude extracts and chromatographic fractions.

Selection of metalloenzymes by catalytic activity using phage display and catalytic elution.

The metallo-beta-lactamase betaLII from Bacillus cereus 569/H/9 was displayed on the filamentous phage fd. The phage-bound enzyme fd-betaLII was shown to be active on benzylpenicillin as substrate; it could be inactivated by complexation of the essential zinc(II) ion with EDTA and reactivated by addition of a zinc(II) salt. A selection process was designed to extract active phage-bound enzymes from libraries of mutants in three steps: 1. inactivation of active phage-bound enzymes by metal ion complexation, 2. binding to substrate-coated magnetic beads, 3. release of phages capable of transforming the substrate into product upon zinc salt addition. The selection process was first successfully tested on model mixtures containing fd-betaLII plus either a dummy phage, a phage displaying an inactive mutant of the serine beta-lactamase TEM-1, or inactive and low-activity mutants of betaLII. The selection was then applied to extract active phage-bound enzymes from a library of mutants generated by mutagenic polymerase chain reaction (PCR). The activity of the library was shown to increase 60-fold after two rounds of selection. Eleven clones from the second round were randomly picked for sequencing and to characterize their activity and stability.

[Anatomic and clinical features of a case of synoviosarcoma]. / Particularités anatomo-cliniques d'un cas de synoviosarcome.

An asymptomatic patient presented a pulmonary metastatis of a synovial sarcoma 15 years after resection of the primary tumor localized in the right groin area. The pathology findings demonstrated the non-specific variable nature of the biphasic epithelial and mesenchymatous feature of such tumors. No treatment was initiated and the patient has remained asymptomatic after five years follow-up. Lack of change in the radiological images led us to re-examine the prognosis and treatment in light of data in the literature.

Display of active subtilisin 309 on phage: analysis of parameters influencing the selection of subtilisin variants with changed substrate specificity from libraries using phosphonylating inhibitors.

Many attempts have been made to endow enzymes with new catalytic activities. One general strategy involves the creation of random combinatorial libraries of mutants associated with an efficient screening or selection scheme. Phage display has been shown to greatly facilitate the selection of polypeptides with desired properties by establishing a close link between the polypeptide and the gene that encodes it. Selection of phage displayed enzymes for new catalytic activities remains a challenge. The aim of this study was to display the serine protease subtilisin 309 (savinase) from Bacillus lentus on the surface of filamentous fd phage and to develop selection schemes that allow the extraction of subtilisin variants with a changed substrate specificity from libraries. Subtilisins are produced as secreted preproenzyme that mature in active enzyme autocatalytically. They have a broad substrate specificity but exhibit a significant preference for hydrophobic residues and very limited reactivity toward charged residues at the P4 site in the substrate. Here, we show that savinase can be functionally displayed on phage in the presence of the proteic inhibitor CI2. The free enzyme is released from its complex with CI2 upon addition of the anionic detergent LAS. The phage-enzyme can be panned on streptavidin beads after labelling by reaction with (biotin-N-epsilon-aminocaproyl-cystamine-N'-glutaryl)-l-Ala-l-Ala-l-P ro-Phe(P)-diphenyl ester. Reactions of libraries, in which residues 104 and 107 forming part of the S4 pocket have been randomised, with (biotin-N-epsilon-aminocaproyl-cystamine-N'-glutaryl)-alpha-l-Lys-l-A la-l-Pro-Phe(P)-diphenylester allowed us to select enzymes with increased specific activity for a substrate containing a lysine in P4. Parameters influencing the selection as for instance the efficiency of maturation of mutant enzymes in libraries have been investigated.

Selection of beta-lactamases and penicillin binding mutants from a library of phage displayed TEM-1 beta-lactamase randomly mutated in the active site omega-loop.

A combinatorial library of mutants of the phage displayed TEM-1 lactamase was generated in the region encompassing residues 163 to 171 of the active site Omega-loop. Two in vitro selection protocols were designed to extract from the library phage-enzymes characterised by a fast acylation by benzyl-penicillin (PenG) to yield either stable or very unstable acyl-enzymes. The critical step of the selections was the kinetically controlled labelling of the phages by reaction with either a biotinylated penicillin derivative or a biotinylated penicillin sulfone, i.e. a beta-lactamase suicide substrate; the biotinylated phages were recovered by panning on immobilised streptavidin. As labelling with biotinylated suicide substrates tends to select enzymes that do not turnover, a counter-selection against penicillin binding mutants was introduced to extract the beta-lactamases. The selected phage-enzymes were characterised by sequencing to identify conserved residues and by kinetic analysis of the reaction with benzyl-penicillin. Several penicillin binding mutants, in which the essential Glu166 is replaced by Asn, were shown to be acylated very fast by PenG, the acylation being characterised by biphasic kinetics. These data are interpreted by a kinetic scheme in which the enzymes exist in two interconvertible conformations. The rate constant of the conformational change suggests that it involves an isomerisation of the peptide bond between residues 166 and 167 and controls a conformation of the Omega-loop compatible with fast acylation of the active site serine residue.

Histidine modification and mutagenesis point to the involvement of a large conformational change in the mechanism of action of phage lambda lysozyme.

Phage lambda lysozyme (lambdaL) is structurally related to other known lysozymes but its mechanism of action is different from the classical lysozyme mechanism, acting as a transglycosidase rather than a hydrolase. As two conformations have been revealed by the crystal structure, we investigated the effect of mutating and modifying a histidine located near to or far from the active site in the respective closed and open conformations. Whereas its asparagine mutation has little or no effect on activity, its N-carbethoxylation inactivates the enzyme. This provide further evidence for the involvement of the closed conformation and for the need of conformational mobility in lambdaL function.

The incorporation of a non-natural amino acid (aza-tryptophan) may help to crystallize a protein and to solve its crystal structure. Application to bacteriophage lambda lysozyme.

Until now, wild-type bacteriophage lambda lysozyme had been impossible to crystallize. This difficulty could be overcome by the replacement of the four tryptophan residues by aza-tryptophans. Analysis of the intermolecular and intramolecular contacts in this modification allows understanding of the differences in behaviour between the native and modified molecules. Furthermore, this mutation was very useful for the creation of new heavy-atom binding sites and for the solution of the non-crystallographic symmetry, which is extremely important for phase improvement. This procedure seems to be generally applicable, at least in the search for new possibilities for heavy-atom binding sites.

Engineering a regulatable enzyme for homogeneous immunoassays.

We have engineered the phage displayed TEM-1 beta-lactamase to generate enzymes that can be used in homogeneous immunoassays because their activity can be modulated by binding to monoclonal antibodies (Mabs) raised against an unrelated protein. Random peptide libraries were genetically inserted into three loops to create hybrid enzymes with binding sites for Mabs. Insertion points were chosen to be close enough to the active site that complex formation could affect the activity. The antibiotic resistance provided by the beta-lactamase activity was used to select the clones encoding active enzymes. Biopanning of the active libraries on immobilized Mabs against the prostate specific antigen (PSA) or on streptavidin yielded enzymes with binding sites for these proteins. Their activity could be regulated by Mab or streptavidin binding. The dissociation constants of the complexes are in the 10(-9) to 10(-6) M range. In a competitive assay, PSA could be detected at a minimal concentration of 10(-9) M. The Mabs recognize mimotopes as no sequence similarity was found between inserts in regulated clones and fragments of the PSA sequence. The method can be developed to generate signaling molecules to be used for the detection of analytes in solution without identification of the epitope.

Bronchial stenosis and sclerosing mediastinitis: an uncommon complication of external thoracic radiotherapy.

The side-effects of radiation therapy on the bronchial tree or on the mediastinum are seldom reported. In this setting, we report a case of sclerosing mediastinitis with bronchial stenosis discovered 1 yr after external radiotherapy for lung cancer. The patient was treated with a Dumont stent and has so far had an uneventful further course for up to 42 months. Bronchial stenosis related to mediastinal fibrosis after radiotherapy has not been reported previously.

Incorporation of 1,2,4-triazole-3-alanine into a mutant of phage lambda lysozyme containing a single histidine.

The only histidine residue in the H31N-H137N double mutant of phage lambda lysozyme (lambdaL), at position 48, was biosynthetically replaced by the analogue 1,2,4-triazole-3-alanine (Taz), the basicity of which is 3 pKa units lower. A histidine-auxotrophic strain was grown to stationary phase by histidine limitation in a synthetic medium, then Taz was added on induction to produce a lysozyme with approximately 75% incorporation. The Taz-containing enzyme precipitated selectively from the cytoplasm and was purified after renaturation. Replacement by Taz had only very minor effects on the activity-pH profile of the enzyme, in contrast with the great perturbations observed for the Asn48 mutant. The relative stabilities of the His48-lambdaL and Taz48-lambdaL mutants were also studied as a function of pH; the results are discussed with regard to the poor accessibility of His48, the low basicity of Taz and the hydrogen bonding patterns suggested by the crystal structure. At neutral pH, Taz48-lambdaL is less stable than His48-lambdaL by approximately 3.5 kcal/mol, probably as a result of the loss of a hydrogen bond in the native form of Taz48-lambdaL. Lowering the pH leads to a progressive stabilization of Taz48-lambdaL relative to His48-lambdaL because of the abnormally low pKa of His48 in the native form of His48-lambdaL.

[Chronic eosinophilic pneumopathy in a black African patient]. / Pneumopathie chronique à éosinophiles chez un patient Africain de race noire.

The authors report a case of a black African patient who suffers from a chronic eosinophilic pneumonia. In view of the lack of precise reporting in the literature of such a case in black Africans, the initial difficulty of strictly excluding a parasitologic etiology is discussed. From the comparison of paraclinical and clinical data with those of the literature, the authors emphasize the close relationship between asthma and chronic eosinophilic pneumonia and the role of alveolar eosinophils in the physiopathology of that illness.

Crystal structure of the lysozyme from bacteriophage lambda and its relationship with V and C-type lysozymes.

Like other lysozymes, the bacteriophage lambda lysozyme is involved in the digestion of bacterial walls. This enzyme is remarkable in that its mechanism of action is different from the classical lysozyme's mechanism. From the point of view of protein evolution, it shows features of lysozymes from different classes. The crystal structure of the enzyme in which all tryptophan residues have been replaced by aza-tryptophan has been solved by X-ray crystallography at 2.3 A using a combination of multiple isomorphous replacement, non-crystallographic symmetry averaging and density modification techniques. There are three molecules in the asymmetric unit. The characteristic structural elements of lysozymes are conserved: each molecule is organized in two domains connected by a helix and the essential catalytic residue (Glu19) is located in the depth of a cleft between the two domains. This cleft shows an open conformation in two of the independent molecules, while access to the cavity is much more restricted in the last one. A structural alignment with T4 lysozyme and hen egg white lysozyme allows us to superpose about 60 C alpha atoms with a rms distance close to 2 A. The best alignments concern the helix preceding the catalytic residue, some parts of the beta sheets and the helix joining the two domains. The results of sequence alignments with the V and C lysozymes, in which weak local similarities had been detected, are compared with the structural results.