Rep protein accommodates together dsDNA and ssDNA which enables a loop-back mechanism to plasmid DNA replication initiation

For DNA replication initiation in Bacteria, replication initiation proteins bind to double-stranded DNA (dsDNA) and interact with single-stranded DNA (ssDNA) at the replication origin. The structural-functional relationship of the nucleoprotein complex involving initiator proteins is still elusive and different models are proposed. In this work, based on crosslinking combined with mass spectrometry (MS), the analysis of mutant proteins and crystal structures, we defined amino acid residues essential for the interaction between plasmid Rep proteins, TrfA and RepE, and ssDNA. This interaction and Rep binding to dsDNA could not be provided in trans, and both are important for dsDNA melting at DNA unwinding element (DUE). We solved two crystal structures of RepE: one in a complex with ssDNA DUE, and another with both ssDNA DUE and dsDNA containing RepE-specific binding sites (iterons). The amino acid residues involved in interaction with ssDNA are located in the WH1 domain in stand β1, helices α1 and α2 and in the WH2 domain in loops preceding strands β1' and β2' and in these strands. It is on the opposite side compared to RepE dsDNA-recognition interface. Our data provide evidence for a loop-back mechanism through which the plasmid replication initiator molecule accommodates together dsDNA and ssDNA.

Structures of pMV158 replication initiator RepB with and without DNA reveal a flexible dual-function protein

DNA replication is essential to all living organisms as it ensures the fidelity of genetic material for the next generation of dividing cells. One of the simplest replication initiation mechanisms is the rolling circle replication. In the streptococcal plasmid pMV158, which confers antibiotic resistance to tetracycline, replication initiation is catalysed by RepB protein. The RepB N-terminal domain or origin binding domain binds to the recognition sequence (bind locus) of the double-strand origin of replication and cleaves one DNA strand at a specific site within the nic locus. Using biochemical and crystallographic analyses, here we show how the origin binding domain recognises and binds to the bind locus using structural elements removed from the active site, namely the recognition α helix, and a β-strand that organises upon binding. A new hexameric structure of full-length RepB that highlights the great flexibility of this protein is presented, which could account for its ability to perform different tasks, namely bind to two distinct loci and cleave one strand of DNA at the plasmid origin.

Modeling and Optimization of β-Galactosidase Entrapping in Polydimethylsiloxane-Modified Silica Composites

Protein entrapment has multiple applications in enzymatic hydrolysis, drug delivery, etc. Here, we report the studies that successfully utilized the Box–Behnken design to model and optimize the parameters of β-galactosidase entrapment in sol–gel-derived silica composites. We have also demonstrated the influence of polymer–polydimethylsiloxane as a composite modifying agent on the activity of entrapped enzymes. We have determined how different sol-gel process parameters influence the activity of entrapped enzymes. The highest impact on β-galactosidase activity was exerted by the water:tetramethoxysilane ratio, followed by polydimethylsiloxane content. Optimized synthesis parameters have been utilized to obtain a composite with maximum β-galactosidase activity. Performed porosity studies have shown that the addition of polydimethylsiloxane increased the pore diameter. Microscopy studies demonstrated that polydimethylsiloxane-modified composites are softer and less rough. Studies of β-galactosidase activity using the o-NPG test showed statistically significant shifts in the enzyme temperature and pH profiles compared to the soluble form. An improvement in the reusability of the enzyme and a significant increase in the thermal stability was also observed. When lactose was used, a strong correlation was observed between the substrate concentration and the type of the catalyzed reaction. Moreover, we have demonstrated that the yields and rates of both lactose hydrolysis and galactooligosaccharides formation were correlated with reaction temperature and with the presence of polydimethylsiloxane. All these findings provide the opportunity for industrial use of optimized PDMS-modified silica composites in lactose elimination from dairy products, e.g., milk or whey.

Defining a novel domain that provides an essential contribution to site-specific interaction of Rep protein with DNA

An essential feature of replication initiation proteins is their ability to bind to DNA. In this work, we describe a new domain that contributes to a replication initiator sequence-specific interaction with DNA. Applying biochemical assays and structure prediction methods coupled with DNA–protein crosslinking, mass spectrometry, and construction and analysis of mutant proteins, we identified that the replication initiator of the broad host range plasmid RK2, in addition to two winged helix domains, contains a third DNA-binding domain. The phylogenetic analysis revealed that the composition of this unique domain is typical within the described TrfA-like protein family. Both in vitro and in vivo experiments involving the constructed TrfA mutant proteins showed that the newly identified domain is essential for the formation of the protein complex with DNA, contributes to the avidity for interaction with DNA, and the replication activity of the initiator. The analysis of mutant proteins, each containing a single substitution, showed that each of the three domains composing TrfA is essential for the formation of the protein complex with DNA. Furthermore, the new domain, along with the winged helix domains, contributes to the sequence specificity of replication initiator interaction within the plasmid replication origin.

European Hernia Society guidelines on prevention and treatment of parastomal hernias

BACKGROUND

International guidelines on the prevention and treatment of parastomal hernias are lacking. The European Hernia Society therefore implemented a Clinical Practice Guideline development project.

METHODS

The guidelines development group consisted of general, hernia and colorectal surgeons, a biostatistician and a biologist, from 14 European countries. These guidelines conformed to the AGREE II standards and the GRADE methodology. The databases of MEDLINE, CINAHL, CENTRAL and the gray literature through OpenGrey were searched. Quality assessment was performed using Scottish Intercollegiate Guidelines Network checklists. The guidelines were presented at the 38th European Hernia Society Congress and each key question was evaluated in a consensus voting of congress participants.

RESULTS

End colostomy is associated with a higher incidence of parastomal hernia, compared to other types of stomas. Clinical examination is necessary for the diagnosis of parastomal hernia, whereas computed tomography scan or ultrasonography may be performed in cases of diagnostic uncertainty. Currently available classifications are not validated; however, we suggest the use of the European Hernia Society classification for uniform research reporting. There is insufficient evidence on the policy of watchful waiting, the route and location of stoma construction, and the size of the aperture. The use of a prophylactic synthetic non-absorbable mesh upon construction of an end colostomy is strongly recommended. No such recommendation can be made for other types of stomas at present. It is strongly recommended to avoid performing a suture repair for elective parastomal hernia. So far, there is no sufficient comparative evidence on specific techniques, open or laparoscopic surgery and specific mesh types. However, a mesh without a hole is suggested in preference to a keyhole mesh when laparoscopic repair is performed.

CONCLUSION

An evidence-based approach to the diagnosis and management of parastomal hernias reveals the lack of evidence on several topics, which need to be addressed by multicenter trials. Parastomal hernia prevention using a prophylactic mesh for end colostomies reduces parastomal herniation. Clinical outcomes should be audited and adverse events must be reported.

Handcuffing reversal is facilitated by proteases and replication initiator monomers

Specific nucleoprotein complexes are formed strictly to prevent over-initiation of DNA replication. An example of those is the so-called handcuff complex, in which two plasmid molecules are coupled together with plasmid-encoded replication initiation protein (Rep). In this work, we elucidate the mechanism of the handcuff complex disruption. In vitro tests, including dissociation progress analysis, demonstrate that the dimeric variants of plasmid RK2 replication initiation protein TrfA are involved in assembling the plasmid handcuff complex which, as we found, reveals high stability. Particular proteases, namely Lon and ClpAP, disrupt the handcuff by degrading TrfA, thus affecting plasmid stability. Moreover, our data demonstrate that TrfA monomers are able to dissociate handcuffed plasmid molecules. Those monomers displace TrfA molecules, which are involved in handcuff formation, and through interaction with the uncoupled plasmid replication origins they re-initiate DNA synthesis. We discuss the relevance of both Rep monomers and host proteases for plasmid maintenance under vegetative and stress conditions.

Thromboelastographic profile of goat blood after the experimental injury of the femoral artery and use of QuikClot gauze and Celox gauze dressings

The aim of this study was to evaluate the suitability of thromboelastometry for the analysis of blood test results in goats after the use of hemostatic dressings to control massive bleeding. The study was carried out on 12 goats, 6 animals in each of two subgroups. In all experimental animals incision of the femoral artery was performed, and bleeding was controlled with QuikClot gauze in the first group and Celox gauze in the second group. Dressings were applied for 60 minutes. Blood samples for thromboelastometry were collected from the jugular vein before the incision and 60 min after the application of a dressing. Clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF) and α angle (°) were measured in three standard ROTEM assays (system with generation of reaction curve, numerical parameters and size of the blood clot): intrinsic coagulation pathway (INTEM), extrinsic coagulation pathway (EXTEM) and functional fibrinogen (FIBTEM). Complete hemostasis of the injured femoral artery was found in all goats. No significant differences between pre- and post-incision thromboelastometric parameters were found in any tests in any of the groups, which indicates that the use of dressings was not associated with blood coagulation disorders. This study is the first to describe the use of thromboelastometry in goats for the assessment of clot formation and hemostatic disorders.

Prophylactic mesh to prevent parastomal hernia after end colostomy: a meta-analysis and trial sequential analysis

PURPOSE

Prevention of parastomal hernia (PSH) formation is crucial, given the high prevalence and difficulties in the surgical repair of PSH. To investigate the effect of a preventive mesh in PSH formation after an end colostomy, we aimed to meta-analyze all relevant randomized controlled trials (RCTs).

METHODS

We searched five databases. For each trial, we extracted risk ratios (RRs) of the effects of mesh or no mesh. The primary outcome was incidence of PSH with a minimum follow-up of 12 months with a clinical and/or computed tomography diagnosis. RRs were combined using the random-effect model (Mantel-Haenszel). To control the risk of type I error, we performed a trial sequential analysis (TSA).

RESULTS

Seven RCTs with low risk of bias (451 patients) were included. Meta-analysis for primary outcome showed a significant reduction of the incidence of PSH using a mesh (RR 0.43, 95% CI 0.26-0.71; P = 0.0009). Regarding TSA calculation for the primary outcome, the accrued information size (451) was 187.1% of the estimated required information size (RIS) (241). Wound infection showed no statistical differences between groups (RR 0.77, 95% CI 0.39-1.54; P = 0.46). PSH repair rate showed a significant reduction in the mesh group (RR 0.28 (95% CI 0.10-0.78; P = 0.01).

CONCLUSIONS

PSH prevention with mesh when creating an end colostomy reduces the incidence of PSH, the risk for subsequent PSH repair and does not increase wound infections. TSA shows that the RIS is reached for the primary outcome. Additional RCTs in the previous context are not needed.

The New 3D Printed Left Atrial Appendage Closure with a Novel Holdfast Device: A Pre-Clinical Feasibility Animal Study

INTRODUCTION

Many patients undergoing cardiac surgery have risk factors for both atrial fibrillation (AF) and stroke. The left atrial appendage (LAA) is the primary site for thrombi formation. The most severe complication of emboli derived from LAA is stroke, which is associated with a 12-month mortality rate of 38% and a 12-month recurrence rate of 17%. The most common form of treatment for atrial fibrillation and stroke prevention is the pharmacological therapy with anticoagulants. Nonetheless this form of therapy is associated with high risk of major bleeding. Therefore LAA occlusion devices should be tested for their ability to reduce future cerebral ischemic events in patients with high-risk of haemorrhage.

AIM

The aim of this study was to evaluate the safety and feasibility of a novel left atrial appendage exclusion device with a minimally invasive introducer in a swine model.

MATERIALS AND METHODS

A completely novel LAA device, which is composed of two tubes connected together using a specially created bail, was designed using finite element modelling (FEM) to obtain an optimal support force of 36 N at the closure line. The monolithic form of the occluder was obtained by using additive manufacturing of granular PA2200 powder with the technology of selective laser sintering (SLS). Fifteen swine were included in the feasibility tests, with 10 animals undergoing fourteen days of follow-up and 5 animals undergoing long-term observation of 3 months. For one animal, the follow-up was further prolonged to 6 months. The device was placed via minithoracotomy. After the observation period, all of the animals were euthanized, and their hearts were tested for LAA closure and local inflammatory and tissue response.

RESULTS

After the defined observation period, all fifteen hearts were explanted. In all cases the full closure of the LAA was achieved. The macroscopic and microscopic evaluation of the explanted hearts showed that all devices were securely integrated in the surrounding tissues. No pericarditis or macroscopic signs of inflammation at the site of the device were found. All pigs were in good condition with normal weight gain and no other clinical symptoms.

CONCLUSION

This novel 3D printed left atrial appendage closure technique with a novel holdfast device was proven to be safe and feasible in all pigs. A benign healing process without inflammation and damage to the surrounding structures or evidence of new thrombi formation was observed. Moreover, the uncomplicated survival and full LAA exclusion in all animals demonstrate the efficacy of this novel and relatively cheap device. Further clinical evaluation and implementation studies should be performed to introduce this new technology into clinical practice.

Sequence-specific interactions of Rep proteins with ssDNA in the AT-rich region of the plasmid replication origin

The DNA unwinding element (DUE) is a sequence rich in adenine and thymine residues present within the origin region of both prokaryotic and eukaryotic replicons. Recently, it has been shown that this is the site where bacterial DnaA proteins, the chromosomal replication initiators, form a specific nucleoprotein filament. DnaA proteins contain a DNA binding domain (DBD) and belong to the family of origin binding proteins (OBPs). To date there has been no data on whether OBPs structurally different from DnaA can form nucleoprotein complexes within the DUE. In this work we demonstrate that plasmid Rep proteins, composed of two Winged Helix domains, distinct from the DBD, specifically bind to one of the strands of ssDNA within the DUE. We observed nucleoprotein complexes formed by these Rep proteins, involving both dsDNA containing the Rep-binding sites (iterons) and the strand-specific ssDNA of the DUE. Formation of these complexes required the presence of all repeated sequence elements located within the DUE. Any changes in these repeated sequences resulted in the disturbance in Rep-ssDNA DUE complex formation and the lack of origin replication activity in vivo or in vitro.

Thoracic endovascular aortic repair with left subclavian artery coverage without prophylactic revascularisation-early and midterm results

Background

The management of the left subclavian artery when coverage is necessary during thoracic aorta endografting remains a matter of debate.

Materials and methods

A retrospective analysis of a single-centre experience with thoracic endovascular aorta repair (TEVAR) was performed. Between April 2004 and October 2012, 125 cases of TEVAR were performed. The analysis focused on patients who required coverage of the left subclavian artery (LSA). We analysed mortality and morbidity with special attention to the rates of cerebrovascular accidents (CVAs) and spinal cord ischaemia (SCI) in the early and midterm.

Results

Of the 125 patients, 53 (42 %, group A) required an intentional coverage of the LSA to obtain an adequate proximal seal for the endograft; the remaining patients constituted group B. None of the patients in group A had protective LSA revascularisation prior to TEVAR. The primary technical success rate was 79.2 vs. 90.3 % (group A vs. group B, p = 0.08), and the primary clinical success rate was 77.4 vs. 82 % (group A vs. group B, p = 0.53). The 30-day mortality rate was 11.3 vs. 11.1 % (group A vs. group B, p = 0.97). The 30-day morbidity was 7.5 vs. 13.9 % (group A vs. group B, p = 0.4). CVA occurred in 1.9 % of group A patients, compared to 1.4 % of patients from group B (p = 0.82). The SCI incidence rate was 0 vs. 1.4 % (p = 0.39). The mean follow-up of group A was 24.1 months (range 2–64.6 months, SD = 19). Additionally, the 1-year estimated survival was 85.5 %, and the 3-year estimated survival was 78 %. There were no midterm CVAs; one event of SCI occurred in the seventh post-operative month in group A.

Conclusion

Our analysis, although retrospective and based on one institution experience, shows a realistic population of TEVAR patients. We prove that TEVAR with coverage of LSA origin can be accomplished with minimal neurological morbidity in this patient population. The study shows that LSA revascularisation is not mandatory before endograft deployment, especially in emergency settings. We also prove that although zone 2 TEVAR extends the proximal landing zone, it does not prevent type IA endoleaks from appearing. A multicentre randomised control trial with higher number of patients is necessary for proper, robust conclusion to be established.

European Hernia Society classification of parastomal hernias

Purpose

A classification of parastomal hernias (PH) is needed to compare different populations described in various trials and cohort studies, complete the previous inguinal and ventral hernia classifications of the European Hernia Society (EHS) and will be integrated into the EuraHS database (European Registry of Abdominal Wall Hernias).

Methods

Several members of the EHS board and invited experts gathered for 2 days to discuss the development of an EHS classification of PH. The discussions were based on a literature review and critical appraisal of existing classifications.

Results

The classification proposal is based on the PH defect size (small is ≤5 cm) and the presence of a concomitant incisional hernia (cIH). Four types were defined: Type I, small PH without cIH; Type II, small PH with cIH; Type III, large PH without cIH; and Type IV, large PH with cIH. In addition, the classification grid includes details about whether the hernia recurs after a previous PH repair or whether it is a primary PH. Clinical validation is needed in the future to assess if the classification allows us to differentiate the treatment strategy and if the classification impacts outcome in these different subgroups.

Conclusion

A classification of PH divided into subgroups according to size and cIH was formulated with the aim of improving the ability to compare different studies and their results.

Physical and mathematical modelling of implant-fascia system in order to improve laparoscopic repair of ventral hernia

BACKGROUND

This paper describes an investigation of biomechanical behaviour of hernia repair, which is focused on the selection of safe linking of certain type of implant with fascia in laparoscopic operation. The strength of various fixations of the implant to the fascia is analysed.

METHODS

The research is based on experimental observations of operated hernia model behaviour during a dynamic impulse load corresponding to post-operative cough. Fifty seven different types of models of implanted mesh are considered. Five types of implants and five types of connectors are used. Mechanical properties of the implants as well as limit tearing forces of joints are identified in uni-axial tensile tests. Mathematical model of implanted mesh based on finite element method is proposed. The identified mechanical properties of the materials are applied and the model is calibrated using quantities measured during experiments.

FINDINGS

The presented results point at trans-abdominal sutures and ProTacks (connectors) and at DynaMesh (implant) as the most reliable materials used in ventral hernia operation, in the tested materials group. Desired properties of implants seem to be: elastic properties similar to the properties of tissues and high local strength, as fixation have a local character. The proposed mathematical model can be applied to simulate real behaviour of an implant with appropriate accuracy and to estimate the number of tacks for the implantation of hernia meshes.

INTERPRETATION

The presented results may help in the deeper understanding of the fascia-mesh system behaviour, and thus may lead to improve the fixation methods.

RK2 plasmid dynamics in Caulobacter crescentus cells--two modes of DNA replication initiation

Undisturbed plasmid dynamics is required for the stable maintenance of plasmid DNA in bacterial cells. In this work, we analysed subcellular localization, DNA synthesis and nucleoprotein complex formation of plasmid RK2 during the cell cycle of Caulobacter crescentus. Our microscopic observations showed asymmetrical distribution of plasmid RK2 foci between the two compartments of Caulobacter predivisional cells, resulting in asymmetrical allocation of plasmids to progeny cells. Moreover, using a quantitative PCR (qPCR) method, we estimated that multiple plasmid particles form a single fluorescent focus and that the number of plasmids per focus is approximately equal in both swarmer and predivisional Caulobacter cells. Analysis of the dynamics of TrfA-oriV complex formation during the Caulobacter cell cycle revealed that TrfA binds oriV primarily during the G1 phase, however, plasmid DNA synthesis occurs during the S and G2 phases of the Caulobacter cell cycle. Both in vitro and in vivo analysis of RK2 replication initiation in C. crescentus cells demonstrated that it is independent of the Caulobacter DnaA protein in the presence of the longer version of TrfA protein, TrfA-44. However, in vivo stability tests of plasmid RK2 derivatives suggested that a DnaA-dependent mode of plasmid replication initiation is also possible.

Five-year results of a randomized clinical trial comparing a polypropylene mesh with a poliglecaprone and polypropylene composite mesh for inguinal hernioplasty

Background

The aim of this study was to assess whether partially absorbable monofilament mesh could influence postoperative pain and recurrence after Lichtenstein hernioplasty over the long term.

Methods

Patients were randomized into two groups that were treated with lightweight (LW) or heavyweight (HW) mesh in 15 centers in Poland. A modified suture technique was used in the lightweight mesh group. Clinical examination was performed. A pain questionnaire was completed five years after the surgery.

Results

Of the 392 patients who underwent surgery, 161 (90.81 %) of 177 in the HW group and 195 (90.69 %) of 215 in the LW group were examined according to protocol, a median of 62 (range 57–66) months after hernia repair. There was no difference in the recurrence rate (1.9 % LW vs. 0.6 % HW; P = 0.493). There were 24 deaths in the follow-up period, but these had no connection to the surgery. The patients treated with LW mesh reported less pain in the early postoperative period. After five years of follow-up, the intensity and the presence of pain did not differ between groups (5 patients in the LW and 4 patients in the HW group). Average pain, (VAS score), was also similar in the LW and HW group (2.25 vs. 2.4) at the fifth year postoperatively.

Conclusion

The use of partially absorbable mesh reduced postoperative pain during the short-term postoperative period. No difference in pain or recurrence rate was observed at 60 months.

DAF- and collagen-binding properties of chimeric Dr fimbriae

Display of heterologous proteins on the surface of micro-organisms has become an increasingly used strategy for a range of applications in microbiology, biotechnology and vaccinology. In this study, the potential of the major structural protein DraE of Escherichia coli Dr fimbriae as a display system for heterologous sequences was tested. One copy of a heterologous sequence mimicking a small P(k) epitope of simian virus 5 was inserted into the draE gene, replacing the N-terminal region of the surface-exposed domain 2 as previously done with the glycoprotein D of herpes simplex virus type 1. The exposure of chimeric proteins on the bacterial surface was detected by immunofluorescence microscopy. Insertion of the heterogenic peptides had no detectable effect on the Ig-barrel structure of the DraE fimbrial subunits, as confirmed by FTIR spectroscopy. Additionally, the affinity of the chimeric fimbriae for DAF and type IV collagen was similar to that of the wild-type Dr fimbriae.

Assessment of usefulness exhibited by different tacks in laparoscopic ventral hernia repair

BACKGROUND

Laparoscopic ventral hernia repair is becoming a popular technique with good results and fast postoperative recovery. The mesh is placed directly under the peritoneum and anchored with transabdominal sutures and tacks. However, the ideal size of the mesh covering the hernia orifice is know, nor the ideal type or amount of tacks has to be described.

METHODS

To assess the forces acting on a single tack, a mathematical model of the ventral hernia was created. The force was described in reference to the surface of the hernia orifice and the pressure in the abdominal cavity. The following different types of mesh were examined in vitro: Proceed (knitted mesh), Dual Mesh (expanded polytetrafluoroethylene [ePTFE] flat mesh), and Shelhigh (biologic flat mesh). The following different tacks also were examined: Protac, Anchor, and EMS. A pig model was used to measure the forces needed to destroy the connection between mesh and tissue and to describe the place of destruction (mesh, tissue, or tack) and the force needed.

RESULTS

The force acting on a single tack proportionally depends on the surface of the hernia orifice and the pressure in the abdominal cavity. The force needed to disconnect the tissue and mesh reached 8.97 +/- 0.11 N for ProTac, 2.67 +/- 0.22 N for Anchor, and 6.67 +/- 1.32 N for EMS. These values do not allow the mesh to be held in the right position when the orifice exceeds 10 cm for Protac and EMS. The disconnection of the EMS and Protac junction damages the tissue. Anchor tacks are insufficient to hold the mesh and stay in the tissue

CONCLUSIONS

In the case of small hernias (diameter<10 cm) EMS or ProTac used alone are not enough to hold the mesh. Anchor is not recommended alone in any hernia.

Structure of DraD invasin from uropathogenicEscherichia coli: a dimer with swapped β-tails

The dra gene cluster of uropathogenic strains of Escherichia coli produces proteins involved in bacterial attachment to and invasion of the eukaryotic host tissues. The crystal structure of a construct of E. coli DraD possessing an additional C-terminal extension of 13 amino acids, including a His6 tag, has been solved at a resolution of 1.05 angstroms. The protein forms symmetric dimers through the exchange of the C-terminal beta-strands, which participate in the immunoglobulin-like beta-sandwich fold of each subunit. This structure confirms that DraD is able to act as an acceptor in the donor-strand complementation mechanism of fiber formation but, in contrast to DraE adhesin, its native sequence does not have a donor strand; therefore, DraD can only be located at the tip of the fiber.

The chaperone-usher pathway of bacterial adhesin biogenesis -- from molecular mechanism to strategies of anti-bacterial prevention and modern vaccine design

The chaperone-usher system determines the biogenesis of surface-exposed adhesive structures responsible for virulence of many Gram-negative bacteria. Investigations of the last 20 years have resolved the mechanism of this pathway on a structural level for different species of pathogenic bacteria. The purpose of this review is to present the molecular mechanisms of the biogenesis of adhesive structures assembled via the chaperone-usher pathway. The obtained mechanistic data allow one to propose potential strategies of anti-bacterial action. Additionally, the specific properties of the polymeric adhesive structures (pili and fimbriae) of the chaperone-usher system allow their use as effective and safe recombinant vaccines carrying foreign epitopes in thousands of copies on bacterial cell surface.

A surface-exposed DraD protein of uropathogenic Escherichia coli bearing Dr fimbriae may be expressed and secreted independently from DraC usher and DraE adhesin

The dra gene cluster, expressed by uropathogenic Escherichia coli strains, determines bacterial attachment and invasion. The Dr fimbrial structures formed at the bacterial cell surface are composed of DraE subunits. The Dr fimbriae-coding cluster contains six open reading frames – draA, draB, draC, draD, draP and draE – among which the draE gene encodes the structural fimbrial subunit DraE. Very little is known about E. coli surface expression of the draD gene product. The expression of DraD and its role in the biogenesis of Dr fimbriae were determined by constructing mutants in the dra operon and by immunoblot and immunofluorescence experiments. In this study, DraD was found to be a surface-exposed protein. The expression of DraD was independent of the DraC usher and DraE fimbrial subunits. Polymerization of DraE fimbrial subunits into fimbrial structures did not require expression of the DraD protein.

The chaperone-usher pathway of bacterial adhesin biogenesis -- from molecular mechanism to strategies of anti-bacterial prevention and modern vaccine design

The chaperone-usher system determines the biogenesis of surface-exposed adhesive structures responsible for virulence of many Gram-negative bacteria. Investigations of the last 20 years have resolved the mechanism of this pathway on a structural level for different species of pathogenic bacteria. The purpose of this review is to present the molecular mechanisms of the biogenesis of adhesive structures assembled via the chaperone-usher pathway. The obtained mechanistic data allow one to propose potential strategies of anti-bacterial action. Additionally, the specific properties of the polymeric adhesive structures (pili and fimbriae) of the chaperone-usher system allow their use as effective and safe recombinant vaccines carrying foreign epitopes in thousands of copies on bacterial cell surface.