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Background: Peptostreptococcus magnus protein L (PpL) is a multidomain, bacterial surface protein whose presence correlates with virulence. It consists of up to five homologous immunoglobulin binding domains that interact with the variable (VL) regions of kappa light chains found on two thirds of mammalian antibodies., Results: We refined the crystal structure of the complex between a human antibody Fab fragment (2A2) and a single PpL domain (61 residues) to 2.7 A. The asymmetric unit contains two Fab molecules sandwiching a single PpL domain, which contacts similar VL framework regions of two light chains via independent interfaces. The residues contacted on VL are remote from the hypervariable loops. One PpL-Vkappa interface agrees with previous biochemical data, while the second is novel. Site-directed mutagenesis and analytical-centrifugation studies suggest that the two PpL binding sites have markedly different affinities for VL. The PpL residues in both interactions are well conserved among different Peptostreptococcus magnus strains. The Fab contact positions identified in the complex explain the high specificity of PpL for antibodies with kappa rather than lambda chains., Conclusions: The PpL-Fab complex shows the first interaction of a bacterial virulence factor with a Fab light chain outside the conventional combining site. Structural comparison with two other bacterial proteins interacting with the Fab heavy chain shows that PpL, structurally homologous to streptococcal SpG domains, shares with the latter a similar binding mode. These two bacterial surface proteins interact with their respective immunoglobulin regions through a similar beta zipper interaction.

Staphylococcus aureus produces a virulence factor, protein A (SpA), that contains five homologous Ig-binding domains. The interactions of SpA with the Fab region of membrane-anchored Igs can stimulate a large fraction of B cells, contributing to lymphocyte clonal selection. To understand the molecular basis for this activity, we have solved the crystal structure of the complex between domain D of SpA and the Fab fragment of a human IgM antibody to 2.7-A resolution. In the complex, helices II and III of domain D interact with the variable region of the Fab heavy chain (V(H)) through framework residues, without the involvement of the hypervariable regions implicated in antigen recognition. The contact residues are highly conserved in human V(H)3 antibodies but not in other families. The contact residues from domain D also are conserved among all SpA Ig-binding domains, suggesting that each could bind in a similar manner. Features of this interaction parallel those reported for staphylococcal enterotoxins that are superantigens for many T cells. The structural homology between Ig V(H) regions and the T-cell receptor V(beta) regions facilitates their comparison, and both types of interactions involve lymphocyte receptor surface remote from the antigen binding site. However, T-cell superantigens reportedly interact through hydrogen bonds with T-cell receptor V(beta) backbone atoms in a primary sequence-independent manner, whereas SpA relies on a sequence-restricted conformational binding with residue side chains, suggesting that this common bacterial pathogen has adopted distinct molecular recognition strategies for affecting large sets of B and T lymphocytes.

In addition to the Cys-Xaa-Xaa-Cys motif at position 30-33, DsbA, the essential catalyst for disulfide bond formation in the bacterial periplasm shares with other oxidoreductases of the thioredoxin family a cis-proline in proximity of the active site residues. In the variant DsbA(P151A), this residue has been changed to an alanine, an almost isosteric residue which is not disposed to adopt the cis conformation. The substitution strongly destabilized the structure of DsbA, as determined by the decrease in the free energy of folding. The pKa of the thiol of Cys30 was only marginally decreased. Although in vivo the variant appeared to be correctly oxidized, it exhibited an activity less than half that of the wild-type enzyme with respect to the folding of alkaline phosphatase, used as a reporter of the disulfide bond formation in the periplasm. DsbA(P151A) crystallized in a different crystal form from the wild-type protein, in space group P2(1) with six molecules in the asymmetric unit. Its X-ray structure was determined to 2.8 A resolution. The most significant conformational changes occurred at the active site. The loop 149-152 adopted a new backbone conformation with Ala151 in a trans conformation. This rearrangement resulted in the loss of van der Waals interactions between this loop and the disulfide bond. His32 from the Cys-Xaa-Xaa-Cys sequence presented in four out of six molecules in the asymmetric unit a gauche conformation not observed in the wild-type protein. The X-ray structure and folding studies on DsbA(P151A) were consistent with the cis-proline playing a major role in the stabilization of the protein. A role for the positioning of the substrate is discussed. These important properties for the enzyme function might explain the conservation of this residue in DsbA and related proteins possessing the thioredoxin fold.

Designing an enzyme requires, among a number of parameters, the appropriate positioning of catalytic machinery within a substrate-binding cleft. Using the structures of cyclophilin-peptide complexes, we have engineered a new catalytic activity into an Escherichia coli cyclophilin by mutating three amino acids, close to the peptide binding cleft, to form a catalytic triad similar to that found in serine proteases. In conjunction with cyclophilin's specificity for proline-bearing peptides, this creates a unique endopeptidase, cyproase 1, which cleaves peptides on the amino-side of proline residues. When acting on an Ala-Pro dipeptide, cyproase 1 has an efficiency (kcat/Km) of 0.7 x 10(4) M(-1) s(-1) and enhances the rate of reaction (kcat/kuncat) 8 x 10(8)-fold. This activity depends upon a deprotonated histidine and is inhibited by nucleophile-specific reagents, as occurs in natural serine proteases. Cyproase 1 can hydrolyse a protein substrate with a proline-specific endoprotease activity.

The x-ray structures of the unliganded esterase-like catalytic antibody D2.3 and its complexes with a substrate analogue and with one of the reaction products are analyzed. Together with the structure of the phosphonate transition state analogue hapten complex, these crystal structures provide a complete description of the reaction pathway. At alkaline pH, D2.3 acts by preferential stabilization of the negatively charged oxyanion intermediate of the reaction that results from hydroxide attack on the substrate. A tyrosine residue plays a crucial role in catalysis: it activates the ester substrate and, together with an asparagine, it stabilizes the oxyanion intermediate. A canal allows facile diffusion of water molecules to the reaction center that is deeply buried in the structure. Residues bordering this canal provide targets for mutagenesis to introduce a general base in the vicinity of the reaction center.

Antibody CNJ206 catalyses the hydrolysis of p-nitrophenyl esters with significant rate enhancement; however, after a few cycles, 90% of the catalytic activity of CNJ206 is irreversibly lost. This report investigates the properties of the inactivated Fab (fragment antigen binding). After inactivation, the residual esterase activity of CNJ206 is similar to that of the catalytic antibody inhibited by the transition-state analogue (TSA) used to elicit it; the affinity of CNJ206 for the TSA is also dramatically lowered. Here we propose a simple scheme that accounts for the steady-state kinetics of inactivation. The following lines of evidence, when taken together, suggest that stable acylated tyrosine side chains within or close to the Fab combining site are involved in the inactivation process: isoelectric focusing and matrix-assisted-laser-desorption-ionisation-time-of-flight (MALDI-TOF) mass spectrometry show that incubation with substrate results in several acylated Fab species; inactivation is stable at pH 8, is reversed by mild hydroxylamine treatment and follows the same kinetics as inhibition of binding, which is slowed down by the presence of the TSA hapten. Analysis of the Fab-TSA X-ray structure shows that three tyrosine residues are potential candidates for the inactivation of CNJ206 by its substrates, Tyr L96 being the most likely one; this also suggests that site-directed mutation of one or more of these residues might prevent substrate inactivation and significantly improve catalysis.

The x-ray structures of three esterase-like catalytic antibodies identified by screening for catalytic activity the entire hybridoma repertoire, elicited in response to a phosphonate transition state analog (TSA) hapten, were analyzed. The high resolution structures account for catalysis by transition state stabilization, and in all three antibodies a tyrosine residue participates in the oxyanion hole. Despite significant conformational differences in their combining sites, the three antibodies, which are the most efficient among those elicited, achieve catalysis in essentially the same mode, suggesting that evolution for binding to a single TSA followed by screening for catalysis lead to antibodies with structural convergence.

Tianeptine, a new antidepressant, has a tricyclic molecular structure. Its main biochemical activity consists of an increase in the reuptake of 5 HT both in men and animals, after acute and chronic administration. Tianeptine demonstrated its antidepressive clinical efficacy in several double-blind versus reference drug trials. A multicentre open trial, including depressed patients enabled us to evaluate the safety of tianeptine and to control the maintenance of the therapeutic efficacy in the course of its long-term prescription. Depressed patients included showed a major depressive episode, single (296.22) or recurrent (296.32) without melancholia or psychotic features, or a dysthymic disorder (300.40), according to DSM III criteria. A minimum MADRS score of a least 25, and the informed consent of the patients were required. The dose of tianeptine was 3 tablets per day (12.5 mg/tablet) with the possibility of increasing to 4 or decreasing to 2 tablets per day, depending on the symptomatology. Therapeutic efficacy was evaluated by item 1 and 2 of the Global Clinical Impression (CGI), the Montgomery and Asberg Depression Rating Scale (MADRS), the Hamilton Anxiety Rating Scale (HARS) and the Hopkins Symptom Check-List (HSCL). Clinical and paraclinical safety were evaluated by CGI item 3, standardized ratings of patients' complaints (CHESS 84), interruption for side effects, evaluation of blood pressure, weight, biological parameters, EKGs. This intermediate evaluation concerns the first 170 depressed patients treated over a one-year period as well as the total group of patients included (n = 447).(ABSTRACT TRUNCATED AT 250 WORDS)

Angular pregnancies which result from implantation of the fertilised oocyte in the mucosa of a uterine horn are very rare. They are usually demonstrated by a picture of rupture which is associated with severe abdominal pain, the syndrome of internal haemorrhage, often a state of shock and all occurring usually between the 6th and the 12th week of pregnancy. Although many authors have shown that there is congenital abnormality of the uterus in these cases this does not always happen and the aetiology of "idiopathic angular pregnancies" is ill understood. The treatment is carried out according to the clinical state: endometrial curettage under laparoscopic control, removal of the uterine horn together with the tube on the same side or even hysterectomy.

Two cases are reported of giant pleural fibroma (2.9 and 4.2 kg), of slow growth (both had been present for 17 years), developing in the parietal pleura in a 56-year-old woman and in the triangular ligament of a 35-year-old man respectively, and treated by surgical excision. Findings in these cases and data on those reported in the literature indicate the principal pathologic and clinical characteristics of these very rare benign tumors of the pleura: onset in the absent of any history of exposure to dust (asbestos); usually fortuitous discovery; suggestive radiological appearances (calcification in some cases) that are not pathognomonic however; differentiation from fibrous mesothelioma by the microscopic or particularly gross pathologic appearance; treatment exclusively surgical and of variable difficulty according to the size of and especially the structures related to the tumor, with the need for careful preoperative screening.

Hyperparathyroidism is a frequent, often fortuitous finding in elderly people. Our series includes 103 patients over 70 years of age, 90 of whom were operated upon. Elderly patients rarely are without any symptom, but it is difficult, prior to surgery, to associate their clinical disorders with hyperparathyroidism. Our results show that surgical treatment is virtually without danger and that most patients were distinctly improved. The innocuousness and effectiveness of surgery in these patients, as well as the absence of medical treatment are as many reasons to widen the indications of the surgical approach.

Benign tumors of the diaphragm are rare lesions. The cystic teratoma of this muscle is an internal axial tumor, a benign dysembryoma, and only 4 cases could be found in the published literature. The cystic teratoma reported was discovered fortuitously during investigation of hypertension. It was located in the diaphragm above the psoas arch.

In an open, clinical trial comprising a total of 49 depressed in-patients, a new selective 5-HT uptake inhibitor citalopram was administered by intravenous infusion in doses of 20-60 mg once daily for per 3 weeks. The therapeutic effect was assessed globally and by means of the CPRS subscale for depression (MADRS). About 40 per cent of the patients showed a complete response whereas about 25 per cent showed a partial response. Side effects which were rated globally and recorded according to a check-list were generally mild and infrequent. The side-effects most frequently observed were tremor, drowsiness, and dizziness which occurred in about 15 per cent of the patients.' Three patients were withdrawn prematurely because of nausea and one because of a skin rash. Cardiovascular recordings were normal except for one patient, who developed a hypertension which may have been related to the test drug. No pathological laboratory values were detected during the trial period. The authors conclude that intravenously administered citalopram is well suited for the treatment of depressed patients.

Since 1969, in a study of 100 patients hospitalized for severe caustic ingestion meeding intensive surgery, the authors have found 9 cases of critical tracheo-bronchic burns characterized by necrotic lesions. Those lesions constitute a severe complication (6 deaths amongst 9 patients) thus the obsolute necessity of precocius and repeated tracheobronchic fiber endoscopies. In case of an ulcerating or pre-splitting aspect appearing in localised necrotic lesions, the authors preconise in emergency a tracheobronchic plasty using a lung patch. Other treatments are discussed.