G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent ...pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Specialty site melanomas on the head and neck, hands and feet, genitalia, and pretibial leg have higher rates of surgical complications after conventional excision with postoperative margin ...assessment (CE-POMA) compared with trunk and proximal extremity melanomas. The rule of 10s describes complication rates after CE-POMA of specialty site melanomas: ∼10% risk for upstaging, ∼10% risk for positive excision margins, ∼10% risk for local recurrence, and ∼10-fold increased likelihood of reconstruction with a flap or graft. Trunk and proximal extremity melanomas encounter these complications at a lower rate, according to the rule of 2s. Mohs micrographic surgery (MMS) with frozen section melanocytic immunostains (MMS-I) and slow Mohs with paraffin sections decrease complications of surgery of specialty site melanomas by detecting upstaging and confirming complete tumor removal with comprehensive microscopic margin assessment before reconstruction. This article reviews information important for counseling melanoma patients about surgical treatment options and for developing consensus guidelines with clear indications for MMS-I or slow Mohs.
Lipidic cubic phase (LCP) crystallization has proven successful for high-resolution structure determination of challenging membrane proteins. Here we present a technique for extruding gel-like LCP ...with embedded membrane protein microcrystals, providing a continuously renewed source of material for serial femtosecond crystallography. Data collected from sub-10-μm-sized crystals produced with less than 0.5 mg of purified protein yield structural insights regarding cyclopamine binding to the Smoothened receptor.
BACKGROUNDIsland pedicle flaps based on a lateral sling of the nasalis have difficulty reaching distal nasal defects due to tethering of the muscle to its insertion point. The authors hypothesized ...that reach could be improved by modifying a crescentic flap to rotate around a pivot point equidistant to the flap and the defect.
OBJECTIVETo describe the design, execution, and results with a modified crescentic island pedicle rotation flap for repair of distal nasal defects after Mohs micrographic surgery.
METHODSThe authors performed a retrospective analysis of patients who had distal nasal defects repaired with a modified crescentic island pedicle rotation flap over an 8-year period. All charts and photographs were examined. Sex and age of the patient, type of cutaneous carcinoma, location and size of the defect, and complications were recorded.
RESULTSForty-eight patients were included. The flap was used to successfully reconstruct defects on the distal nose ranging in size from 0.25 cm to 3.8 cm. Complications involved one wound infection and one episode of postoperative bleeding.
CONCLUSIONThe authorsʼ modifications to the island pedicle flap may be reliably used to reconstruct small- to medium-sized defects of the distal nose in a single stage with minimal risk of complications.
IMPORTANCE: National Comprehensive Cancer Network guidelines for melanoma have consistently recommended wide local excision as the standard of care since their inception. Although surgery with more ...comprehensive margin assessment (eg, Mohs surgery) has been advocated for certain subsets of melanoma, how often these techniques are used in clinical practice is uncertain. OBJECTIVE: To examine trends in the use of comprehensive margin assessment surgery for melanoma by tracking claims data for Mohs surgery. DESIGN, SETTING, AND PARTICIPANTS: This national cross-sectional analysis examined claims data from the Optum Clinformatics Data Mart, a nationally representative database. The study cohort consisted of 79 108 patients undergoing surgical excision for melanoma from January 1, 2001, through December 31, 2016. Data were analyzed from January 1, 2001, through December 31, 2016. MAIN OUTCOMES AND MEASURES: The primary outcome was the likelihood of a melanoma being treated with Mohs surgery over time, evaluated by multivariable logistic regression and expressed as the odds of treatment per additional calendar year. RESULTS: Among 79 108 patients with melanoma (median age, 63 years interquartile range {IQR}, 51-73; 47 407 men 59.9%), 75 047 were treated with conventional excision (median age, 62 years IQR, 50-73 years; 44 786 men 59.7%) and 4061 with Mohs surgery (median age, 67 years IQR, 56-76 years; 2621 men 64.5%). Mohs surgery was used in 5.1% of all surgical cases, with the rate of Mohs surgery increasing 304% from 2.6% in 2001 to 7.9% in 2016. Odds of receiving Mohs surgery for melanoma increased significantly in more recent calendar years (odds ratio OR, 1.02 per calendar year; 95% CI, 1.01-1.03; P < .001). Immunohistochemistry (IHC) use was only coded with Mohs surgery in 1087 cases (26.8%), and the odds of receiving Mohs surgery with IHC increased in more recent calendar years (OR, 1.13 per calendar year; 95% CI, 1.10-1.15; P < .001). Use of Mohs surgery and Mohs surgery with IHC for melanoma differed widely across geographic census divisions with greater than 3-fold variation between the regions with highest and lowest use in every period (eg, for 2013 through 2016, the East South Central region used Mohs surgery in 8.8% of melanoma excisions compared with 2.6 in the New England region). CONCLUSIONS AND RELEVANCE: Despite stable guidelines for melanoma surgery, the results of this study suggest that surgical practices for melanoma are evolving. Wide variations in surgical practice patterns for melanoma are present in the United States. This study’s findings suggest that the effect of variations in surgical techniques on outcomes requires scrutiny and further study.
As a protective envelope surrounding the bacterial cell, the peptidoglycan sacculus is a site of vulnerability and an antibiotic target. Peptidoglycan components, assembled in the cytoplasm, are ...shuttled across the membrane in a cycle that uses undecaprenyl-phosphate. A product of peptidoglycan synthesis, undecaprenyl-pyrophosphate, is converted to undecaprenyl-phosphate for reuse in the cycle by the membrane integral pyrophosphatase, BacA. To understand how BacA functions, we determine its crystal structure at 2.6 Å resolution. The enzyme is open to the periplasm and to the periplasmic leaflet via a pocket that extends into the membrane. Conserved residues map to the pocket where pyrophosphorolysis occurs. BacA incorporates an interdigitated inverted topology repeat, a topology type thus far only reported in transporters and channels. This unique topology raises issues regarding the ancestry of BacA, the possibility that BacA has alternate active sites on either side of the membrane and its possible function as a flippase.
We describe a data collection method that uses a single crystal to solve X-ray structures by native SAD (single-wavelength anomalous diffraction). We solved the structures of 11 real-life examples, ...including a human membrane protein, a protein-DNA complex and a 266-kDa multiprotein-ligand complex, using this method. The data collection strategy is suitable for routine structure determination and can be implemented at most macromolecular crystallography synchrotron beamlines.
The lipid-based bicontinuous cubic mesophase is a nanoporous membrane mimetic with applications in areas that include medicine, personal care products, foods and the basic sciences. An application of ...particular note concerns it use as a medium in which to grow crystals of membrane proteins for structure determination by X-ray crystallography. At least two variations of the mesophase exist. One is the highly viscous cubic phase, which has well developed long-range order. The other so-called sponge phase is considerably more fluid and lacks long-range order. The sponge phase has recently been shown to be a convenient vehicle for delivering microcrystals of membrane proteins to an X-ray free-electron laser beam for serial femtosecond crystallography (SFX). Unfortunately, the sponge phase approach calls for large amounts of protein that are not always available in the case of membrane proteins. The cubic phase offers the advantage of requiring significantly less protein for SFX but comes with its own challenges. Here, we describe the physico-chemical bases for these challenges, solutions to them and prospects for future uses of lipidic mesophases in the SFX arena.
Diacylglycerol kinase catalyses the ATP-dependent conversion of diacylglycerol to phosphatidic acid in the plasma membrane of Escherichia coli. The small size of this integral membrane trimer, which ...has 121 residues per subunit, means that available protein must be used economically to craft three catalytic and substrate-binding sites centred about the membrane/cytosol interface. How nature has accomplished this extraordinary feat is revealed here in a crystal structure of the kinase captured as a ternary complex with bound lipid substrate and an ATP analogue. Residues, identified as essential for activity by mutagenesis, decorate the active site and are rationalized by the ternary structure. The γ-phosphate of the ATP analogue is positioned for direct transfer to the primary hydroxyl of the lipid whose acyl chain is in the membrane. A catalytic mechanism for this unique enzyme is proposed. The active site architecture shows clear evidence of having arisen by convergent evolution.
Obtaining rapid and effective hemostasis Howe, Nicole, MD; Cherpelis, Basil, MD
Journal of the American Academy of Dermatology,
November 2013, Letnik:
69, Številka:
5
Journal Article
Recenzirano
Effective and rapid hemostasis is critical to optimize surgical outcomes. An advantageous adjunct in accelerating the clotting process during dermatologic surgery is the use of topical hemostatic ...agents, which allow dermatologic surgeons to quickly clear the surgical field while avoiding the adverse effects of systemic medications. The growing rate of patients with pacemakers and defibrillators limits the possibility of electrosurgery. It is not unusual for patients to be taking ≥1 anticoagulant medication(s). For these reasons, the use of topical hemostatic agents is likely to gain more recognition in the literature. The term topical hemostatic agents encompasses an array of pharmacotherapies, sealants, adhesives, absorbable agents, biologics, and combination products. The optimal use of topical hemostatic agents demands that dermatologic surgeons be familiar with each of these options, because the type of product used must be selected based on surgical location, wound size, and the extent of bleeding. With few randomized controlled trials in existence reviewing the efficacy of these medications, the subject of topical styptic agents has largely gone unstudied. Part I of this continuing medical education article reviews the available topical hemostatic agents and the ideal clinical settings for their use.
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