A Rapid Cloning Method Employing Orthogonal End Protection

We describe a novel in vitro cloning strategy that combines standard tools in molecular biology with a basic protecting group concept to create a versatile framework for the rapid and seamless assembly of modular DNA building blocks into functional open reading frames. Analogous to chemical synthesis strategies, our assembly design yields idempotent composite synthons amenable to iterative and recursive split-and-pool reaction cycles. As an example, we illustrate the simplicity, versatility and efficiency of the approach by constructing an open reading frame composed of tandem arrays of a human fibronectin type III (FNIII) domain and the von Willebrand Factor A2 domain (VWFA2), as well as chimeric (FNIII)n-VWFA2-(FNIII)n constructs. Although we primarily designed this strategy to accelerate assembly of repetitive constructs for single-molecule force spectroscopy, we anticipate that this approach is equally applicable to the reconstitution and modification of complex modular sequences including structural and functional analysis of multi-domain proteins, synthetic biology or the modular construction of episomal vectors

Crystal structure of quinohemoprotein alcohol dehydrogenase from Comamonas testosteroni - Structural basis for substrate oxidation and electron transfer

Quinoprotein alcohol dehydrogenases are redox enzymes that participate in distinctive catabolic pathways that enable bacteria to grow on various alcohols as the sole source of carbon and energy. The x-ray structure of the quinohemoprotein alcohol dehydrogenase from Comamonas testosteroni has been determined at 1.44 Angstrom resolution. It comprises two domains. The N-terminal domain has a beta-propeller fold and binds one pyrrolo-quinoliue quinone cofactor and one calcium ion in the active site. A tetrahydrofuran-2-carboxylic acid molecule is present in the substrate-binding cleft. The position of this oxidation product provides valuable information on the amino acid residues involved in the reaction mechanism and their function. The C-terminal domain is an a-helical type I cytochrome c with His(608) and Met(647) as heme-iron ligands. This is the first reported structure of an electron transfer system between a quinoprotein alcohol dehydrogenase and cytochrome c. The shortest distance between pyrroloquinoline quinone and heme c is 12.9 Angstrom, one of the longest physiological edge-to-edge distances yet determined between two redox centers. A highly unusual disulfide bond between two adjacent cysteines bridges the redox centers. It appears essential for electron transfer. A water channel delineates a possible pathway for proton transfer from the active site to the solvent.</p

Structure of Complement Component C2a: Implications for Convertase Formation and Substrate Binding

SummaryC2a provides the catalytic center to the convertase complexes of the classical and lectin-binding pathways of complement activation. We determined two crystal structures of full-length C2a, with and without a pseudo ligand bound. Both structures reveal a near-active conformation of the catalytic center of the serine protease domains, while the von Willebrand factor A-type domains display an intermediate activation state of helix α7 with an open, activated metal-ion-dependent adhesion site. The open adhesion site likely serves to enhance the affinity for the ligand C4b, similar to “inside-out” signaling in integrins. Surprisingly, the N-terminal residues of C2a are buried in a crevice near helix α7, indicative of a structural switch between C2 and C2a. Extended loops on the protease domain possibly envelop the protruding anaphylatoxin domain of the substrate C3. Together with a putative substrate-induced completion of the oxyanion hole, this may contribute to the high substrate specificity of the convertases

EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: 2019 update

Objectives: To provide an update of the European League Against Rheumatism (EULAR) rheumatoid arthritis (RA) management recommendations to account for the most recent developments in the field. Methods: An international task force considered new evidence supporting or contradicting previous recommendations and novel therapies and strategic insights based on two systematic literature searches on efficacy and safety of disease-modifying antirheumatic drugs (DMARDs) since the last update (2016) until 2019. A predefined voting process was applied, current levels of evidence and strengths of recommendation were assigned and participants ultimately voted independently on their level of agreement with each of the items. Results: The task force agreed on 5 overarching principles and 12 recommendations concerning use of conventional synthetic (cs) DMARDs (methotrexate (MTX), leflunomide, sulfasalazine); glucocorticoids (GCs); biological (b) DMARDs (tumour necrosis factor inhibitors (adalimumab, certolizumab pegol, etanercept, golimumab, infliximab), abatacept, rituximab, tocilizumab, sarilumab and biosimilar (bs) DMARDs) and targeted synthetic (ts) DMARDs (the Janus kinase (JAK) inhibitors tofacitinib, baricitinib, filgotinib, upadacitinib). Guidance on monotherapy, combination therapy, treatment strategies (treat-to-target) and tapering on sustained clinical remission is provided. Cost and sequencing of b/tsDMARDs are addressed. Initially, MTX plus GCs and upon insufficient response to this therapy within 3 to 6 months, stratification according to risk factors is recommended. With poor prognostic factors (presence of autoantibodies, high disease activity, early erosions or failure of two csDMARDs), any bDMARD or JAK inhibitor should be added to the csDMARD. If this fails, any other bDMARD (from another or the same class) or tsDMARD is recommended. On sustained remission, DMARDs may be tapered, but not be stopped. Levels of evidence and levels of agreement were mostly high. Conclusions: These updated EULAR recommendations provide consensus on the management of RA with respect to benefit, safety, preferences and cost

Association of the OPRM1 Variant rs1799971 (A118G) with Non-Specific Liability to Substance Dependence in a Collaborative de novo Meta-Analysis of European-Ancestry Cohorts

Peer reviewe

Case Reports1. A Late Presentation of Loeys-Dietz Syndrome: Beware of TGFβ Receptor Mutations in Benign Joint Hypermobility

Background: Thoracic aortic aneurysms (TAA) and dissections are not uncommon causes of sudden death in young adults. Loeys-Dietz syndrome (LDS) is a rare, recently described, autosomal dominant, connective tissue disease characterized by aggressive arterial aneurysms, resulting from mutations in the transforming growth factor beta (TGFβ) receptor genes TGFBR1 and TGFBR2. Mean age at death is 26.1 years, most often due to aortic dissection. We report an unusually late presentation of LDS, diagnosed following elective surgery in a female with a long history of joint hypermobility. Methods: A 51-year-old Caucasian lady complained of chest pain and headache following a dural leak from spinal anaesthesia for an elective ankle arthroscopy. CT scan and echocardiography demonstrated a dilated aortic root and significant aortic regurgitation. MRA demonstrated aortic tortuosity, an infrarenal aortic aneurysm and aneurysms in the left renal and right internal mammary arteries. She underwent aortic root repair and aortic valve replacement. She had a background of long-standing joint pains secondary to hypermobility, easy bruising, unusual fracture susceptibility and mild bronchiectasis. She had one healthy child age 32, after which she suffered a uterine prolapse. Examination revealed mild Marfanoid features. Uvula, skin and ophthalmological examination was normal. Results: Fibrillin-1 testing for Marfan syndrome (MFS) was negative. Detection of a c.1270G > C (p.Gly424Arg) TGFBR2 mutation confirmed the diagnosis of LDS. Losartan was started for vascular protection. Conclusions: LDS is a severe inherited vasculopathy that usually presents in childhood. It is characterized by aortic root dilatation and ascending aneurysms. There is a higher risk of aortic dissection compared with MFS. Clinical features overlap with MFS and Ehlers Danlos syndrome Type IV, but differentiating dysmorphogenic features include ocular hypertelorism, bifid uvula and cleft palate. Echocardiography and MRA or CT scanning from head to pelvis is recommended to establish the extent of vascular involvement. Management involves early surgical intervention, including early valve-sparing aortic root replacement, genetic counselling and close monitoring in pregnancy. Despite being caused by loss of function mutations in either TGFβ receptor, paradoxical activation of TGFβ signalling is seen, suggesting that TGFβ antagonism may confer disease modifying effects similar to those observed in MFS. TGFβ antagonism can be achieved with angiotensin antagonists, such as Losartan, which is able to delay aortic aneurysm development in preclinical models and in patients with MFS. Our case emphasizes the importance of timely recognition of vasculopathy syndromes in patients with hypermobility and the need for early surgical intervention. It also highlights their heterogeneity and the potential for late presentation. Disclosures: The authors have declared no conflicts of interes

Apparent melting temperature of concatameric proteins.

<p>Apparent melting temperature of concatameric proteins.</p

Assembly of chimeric constructs and one-pot concatamer formation.

<p>(A) Assembly of (FNIII)₂-VWFA2-(FNIII)₂ sandwich constructs from a modular assembly vector (top). PCR amplification with specific primers (indicated above the lanes; <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037617#pone.0037617.s002" target="_blank">Table S1</a></b>) show that the A2 synthon is sandwiched between two ¹³FNIII repeats. (B) One-pot concatamer formation with orthogonal chain stoppers. Fully deprotected synthons are mixed in different molar ratios with orthogonal chain stoppers (equivalent synthons with protecting groups on one end). Increasing the concentration of chain stoppers shifts the size distribution towards shorter concatamers. Molar ratios of unprotected synthons:chain stoppers are indicated at the top of the lanes. Bands marked with asterisks presumably correspond to circularized dimers.</p

Split-and-pool assembly of DNA synthons.

<p>(A) Entry synthons are flanked on both sides by recognition sequences for the type IIS endonucleases BsaI and BsmBI. Restriction by either BsaI or BsmBI selectively exposes user-definable 4-base cohesive overhang sequences (5′-XXXX vs. 5′-xxxx) at one end of the synthon, while maintaining orthogonal protection groups (with 5′-YYYY vs. 5′-zzzz overhangs) at the opposite end. (B) Schematic representation of the ‘split-and-pool’ assembly principle. Cohesive ends of entry synthons are selectively deprotected by digestion with either BsaI or BsmBI. Pooling of the deprotected synthons in the presence of ligase results in unidirectional assembly, affording an idempotent tandem repeat synthon by restoration of orthogonal protecting groups on opposite ends. Each product module can recursively enter the assembly cycle (left panel) N times to yield concatameric synthons with 2N elements. The same strategy can be applied to the assembly of heterosynthons (dashed box), which allows for the engineering of chimeric and multimodular proteins or polycistronic genes.</p

Efficient synthon assembly with split-and-pool reactions.

<p>(A) Equimolar amounts of BsaI or BsmBI deprotected ¹³FNIII synthons were incubated with 1 unit of T4 ligase and product formation was assessed at different time points (left panel) or after 15 min in buffer conditions with and without 15% (w/v) PEG6000 (right panel). (B) No significant differences in assembly efficiency are observed after 15′ incubation at ligase concentrations ranging from 1 to 10 units. (C) Performance of split-and-pool assembly in comparison to sequential approaches. Within one day the comprehensive series of (¹³FNIII)₁ to (¹³FNIII)₈ repeats can be assembled with the split-and-pool approach (spectrum circles) and ligated into the pShuttle vector. After a single cloning step expression plasmid is obtained on day 3. In comparison, sequential assembly with e.g. the BamHI/BglII system requires 12 days to obtain the (¹³FNIII)₈ construct.</p