A fatal case of Arcanobacterium pyogenes endocarditis in a man with no identified animal contact: case report and review of the literature.

Arcanobacterium pyogenes is a rare cause of infection in humans, mostly related to living in rural areas and to contacts with animals. We describe a case of fatal Arcanobacterium pyogenes endocarditis, confirmed by DNA sequencing, in a patient without typical epidemiological exposure.

Poly(A) polymerase I of Escherichia coli: characterization of the catalytic domain, an RNA binding site and regions for the interaction with proteins involved in mRNA degradation.

Poly(A) polymerase I (PAP I) of Escherichia coli is a member of the nucleotidyltransferase (Ntr) superfamily that includes the eukaryotic PAPs and all the known tRNA CCA-adding enzymes. Five highly conserved aspartic acids in the putative catalytic site of PAP I were changed to either alanine or proline, demonstrating their importance for polymerase activity. A glycine that is absolutely conserved in all Ntrs was also changed yielding a novel mutant protein in which ATP was wastefully hydrolysed in a primer-independent reaction. This is the first work to characterize the catalytic site of a eubacterial PAP and, despite the conservation of certain sequences, we predict that the overall architecture of the eukaryotic and eubacterial active sites is likely to be different. Binding sites for RNase E, a component of the RNA degradosome, and RNA were mapped by North-western and Far-western blotting using truncated forms of PAP I. Additional protein-protein interactions were detected between PAP I and CsdA, RhlE and SrmB, suggesting an unexpected connection between PAP I and these E. coli DEAD box RNA helicases. These results show that the functional organization of PAP I is similar to the eukaryotic PAPs with an N-terminal catalytic domain, a C-terminal RNA binding domain and sites for the interaction with other protein factors.

mRNA degradation. A tale of poly(A) and multiprotein machines.

The Escherichia coli RNA degradosome is a multiprotein complex containing an endoribonuclease, polynucleotide phosphorylase and a DEAD-box RNA helicase. A related complex has been described in the spinach chloroplast. The exosome and the mtEXO complex have recently been described in yeast and it is likely that related complexes also exist in animal cells. This research suggests the widespread existence of sophisticated machines for the efficient degradation of messenger RNA. The DEAD-box helicase in the degradosome can unwind regions of RNA structure that interfere with 3'-5' degradation. The polyadenylation of RNA 3' ends is also known to promote degradation by creating a 'toehold' for the degradation machinery. Much remains to be learned about the regulation of mRNA stability. The complexity of the degradation process, both in the eubacteria and in the eukaryotes, suggests that many steps are possible points of control.

The Bacillus subtilis nucleotidyltransferase is a tRNA CCA-adding enzyme.

There has been increased interest in bacterial polyadenylation with the recent demonstration that 3' poly(A) tails are involved in RNA degradation. Poly(A) polymerase I (PAP I) of Escherichia coli is a member of the nucleotidyltransferase (Ntr) family that includes the functionally related tRNA CCA-adding enzymes. Thirty members of the Ntr family were detected in a search of the current database of eubacterial genomic sequences. Gram-negative organisms from the beta and gamma subdivisions of the purple bacteria have two genes encoding putative Ntr proteins, and it was possible to predict their activities as either PAP or CCA adding by sequence comparisons with the E. coli homologues. Prediction of the functions of proteins encoded by the genes from more distantly related bacteria was not reliable. The Bacillus subtilis papS gene encodes a protein that was predicted to have PAP activity. We have overexpressed and characterized this protein, demonstrating that it is a tRNA nucleotidyltransferase. We suggest that the papS gene should be renamed cca, following the notation for its E. coli counterpart. The available evidence indicates that cca is the only gene encoding an Ntr protein, despite previous suggestions that B. subtilis has a PAP similar to E. coli PAP I. Thus, the activity involved in RNA 3' polyadenylation in the gram-positive bacteria apparently resides in an enzyme distinct from its counterpart in gram-negative bacteria.

Ribonuclease E organizes the protein interactions in the Escherichia coli RNA degradosome.

The Escherichia coli RNA degradosome is the prototype of a recently discovered family of multiprotein machines involved in the processing and degradation of RNA. The interactions between the various protein components of the RNA degradosome were investigated by Far Western blotting, the yeast two-hybrid assay, and coimmunopurification experiments. Our results demonstrate that the carboxy-terminal half (CTH) of ribonuclease E (RNase E) contains the binding sites for the three other major degradosomal components, the DEAD-box RNA helicase RhlB, enolase, and polynucleotide phosphorylase (PNPase). The CTH of RNase E acts as the scaffold of the complex upon which the other degradosomal components are assembled. Regions for oligomerization were detected in the amino-terminal and central regions of RNase E. Furthermore, polypeptides derived from the highly charged region of RNase E, containing the RhlB binding site, stimulate RhlB activity at least 15-fold, saturating at one polypeptide per RhlB molecule. A model for the regulation of the RhlB RNA helicase activity is presented. The description of RNase E now emerging is that of a remarkably complex multidomain protein containing an amino-terminal catalytic domain, a central RNA-binding domain, and carboxy-terminal binding sites for the other major components of the RNA degradosome.

Bacterial poly(A) polymerase: an enzyme that modulates RNA stability.

We have constructed a strain that overexpresses E coli poly(A) polymerase (PAP I). The recombinant protein was soluble, and a partially purified extract had high levels of poly(A) polymerising activity. An antiserum raised against the overexpressed PAP I has permitted two types of analysis: the identification of other E coli proteins that may interact with PAP I, and the search for PAP I-like proteins in other bacteria. Immunoprecipitation experiments suggest that PAP I is associated with a 48-kDa protein. This protein remains to be identified. Western blotting using the antiserum against E coli PAP I revealed related proteins in a variety of Gram-negative bacteria and in B subtilis. A comparison of the E coli protein with putative poly(A) polymerases recently identified in H influenza and B subtilis showed highly conserved sequences in the amino terminal and central portions of the proteins that may be important for enzyme activity.

Fractures of the hip in the elderly: therapeutic and medico-social considerations.

The factors influencing mortality and morbidity were analysed in a series of 224 elderly patients with hip fractures. It was found that mortality was influenced by the high age, the number of medical antecedents and the number of general complications occurring following surgery. Mortality rate was high in mentally deteriorated patients with a gain in autonomy in only 25% of the cases. On the contrary, mortality was less, and there were few modifications of the mental status in patients who were mentally normal upon admission. The recovery of total or partial autonomy in this group was 69.9%, justifying therefore the surgical intervention.

[Role of peridural anesthesia in thoracic surgery]. / Place de l'anesthésie péridurale en chirurgie thoracique

Periduralaneaesthesia by the cervical route (C6-C7 or C7-D1) or by the upper lumbar route with an ascending catheter, permit thoracic surgery in all its applications. The reduction in operative bleeding is an appreciable advantage of the method, and automatic nervous stability is remarkable. On the other hand, keeping the patient in the waking state is a definite disadvantage, especially in removal of one lung. As far as the anaesthetist is concerned he will be faced with difficulties of ventilation and bronchial aspiration. On the other hand, combined with slight general anaesthesia and tracheal intubation, peridural anaesthesia is definitely of interest. Furthermore, during the post-operative period, it is precious permitting a cough without pain and, in this respect, the comparison with anaesthesia of the inter-costal nerves, is worth discussins, each technique having special advantages.