<Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>-purpura fulminans as an invasive form of group A streptococcal infection

Background

Streptococcus pyogenes is an uncommon pathogen of purpura fulminans, and the pathogenesis of S. pyogenes-purpura fulminans remains unclear because of paucity of cases. We reported a pediatric case of S. pyogenes-purpura fulminans with literature review of the disease.

Case presentation

A 3-year-old boy showed limping, lethargy and acral gangrene within 24 h. A diagnosis of S. pyogenes-purpura fulminans was made for bacterial isolation from throat and peripheral blood. Intensive therapy led to a survival with amputation of the left distal metatarsal bone, and normal development. The isolated M12 carried no mutation of csrS/R or rgg. Thrombophilia or immunodeficiency was excluded.

Discussion

Twelve-reported cases (9 pediatric and 3 elderly) of S. pyogenes-purpura fulminans started with shock and coagulopathy. Five patients age <?8 years had no underlying disease and survived. One youngest and two immunocompromised patients died.

Conclusion

Streptococcus pyogenes-acute infectious purpura fulminans is a distinctive rare form of aggressive GAS infections.

     

Negatively Charged Lipids Are Essential for Functional and Structural Switch of Human 2-Cys Peroxiredoxin II

The function of ubiquitous 2-Cys peroxiredoxins (Prxs) can be converted alternatively from peroxidases to molecular chaperones. This conversion has been reported to occur by the formation of high-molecular-weight (HMW) complexes upon overoxidation of or ATP/ADP binding to 2-Cys Prxs, but its mechanism is not well understood. Here, we show that upon binding to phosphatidylserine or phosphatidylglycerol dimeric human 2-Cys PrxII (hPrxII) is assembled to trefoil-shaped small oligomers (possibly hexamers) with full chaperone and null peroxidase activities. Spherical HMW complexes are formed, only when phosphatidylserine or phosphatidylglycerol is bound to overoxidized or ATP/ADP-bound hPrxII. The spherical HMW complexes are lipid vesicles covered with trefoil-shaped oligomers arranged in a hexagonal lattice pattern. Thus, these lipids with a net negative charge, which can be supplied by increased membrane trafficking under oxidative stress, are essential for the structural and functional switch of hPrxII and possibly most 2-Cys Prxs.     

Attempt to simultaneously generate three chiral centers in 4-hydroxyisoleucine with microbial carbonyl reductases

A panel of microorganisms was screened for selective reduction ability towards a racemic mixture of prochiral 2-amino-3-methyl-4-ketopentanoate (rac-AMKP). Several of the microorganisms tested produced greater than 0.5 mM 4-hydroxyisoleucine (HIL) from rac-AMKP, and the stereoselectivity of HIL formation was found to depend on the taxonomic category to which the microorganism belonged. The enzymes responsible for the AMKP-reducing activity, ApAR and FsAR, were identified from two of these microorganisms, Aureobasidium pullulans NBRC 4466 and Fusarium solani TG-2, respectively. Three AMKP reducing enzymes, ApAR, FsAR, and the previously reported BtHILDH, were reacted with rac-AMKP, and each enzyme selectively produced a specific composition of HIL stereoisomers. The enzymes appeared to have different characteristics in recognition of the stereostructure of the substrate AMKP and in control of the 4-hydroxyl group configuration in the HIL product.     

Detection of mammosomatotroph cells and identification of the coexistence of growth hormone and prolactin within the same secretory granules in these cells using confocal laser scanning microscopy

This study was designed to examine whether mammosomatotroph cells (MS cells) can be easily detected using confocal laser scanning microscopy (CLSM) and whether the coexistence of growth hormone (GH) and prolactin (PRL) within the same secretory granule can be identified in the MS cell using CLSM. Conventional epoxy resin-embedded tissues of mixed GH- and PRL-secreting human pituitary adenomas were used for this double-labelling immunofluorescent study by CLSM. A semithin section of the tissue after plastic removal and bleaching was immunohistochemically double-stained with primary antibodies against GH and PRL, followed by secondary antibodies conjugated with Rhodamine (GH) and FITC (PRL). MS cells simultaneously showing fluorescence of both Rhodamine and FITC were easily detected by CLSM at lower magnification. At higher magnification, the coexistence of Rhodamine and FITC on the same secretory granule was identified by using a superimposed display. This finding was confirmed by immunoelectron microscopy. The CLSM technique may be useful for the study of MS cells.     

Structural Insights into the Substrate Specificity Switch Mechanism of the Type III Protein Export Apparatus

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Single-Unit Imaging of Membrane Protein-Embedded Nanodiscs from Two Oriented Sides by High-Speed Atomic Force Microscopy

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CYK4 Promotes Antiparallel Microtubule Bundling by Optimizing MKLP1 Neck Conformation

Centralspindlin, a constitutive 2:2 heterotetramer of MKLP1 (a kinesin-6) and the non-motor subunit CYK4, plays important roles in cytokinesis. It is crucial for the formation of central spindle microtubule bundle structure. Its accumulation at the central antiparallel overlap zone is key for recruitment and regulation of downstream cytokinesis factors and for stable anchoring of the plasma membrane at the midbody. Both MKLP1 and CYK4 are required for efficient microtubule bundling. However, the mechanism by which CYK4 contributes to this is unclear. Here we performed structural and functional analyses of centralspindlin using high-speed atomic force microscopy, Fӧrster resonance energy transfer analysis, and in vitro reconstitution. Our data reveal that CYK4 binds to a globular mass in the atypically long MKLP1 neck domain between the catalytic core and the coiled coil and thereby reconfigures the two motor domains in the MKLP1 dimer to be suitable for antiparallel microtubule bundling. Our work provides insights into the microtubule bundling during cytokinesis and into the working mechanisms of the kinesins with non-canonical neck structures.     

A novel Fe(II)/α‐ketoglutarate‐dependent dioxygenase from Burkholderia ambifaria has β‐hydroxylating activity of N‐succinyl l‐leucine

An Fe(II)/α‐ketoglutarate‐dependent dioxygenase, SadA, was obtained from Burkholderia ambifaria AMMD and heterologously expressed in Escherichia coli. Purified recombinant SadA had catalytic activity towards several N‐substituted l‐amino acids, which was especially strong with N‐succinyl l‐leucine. With the NMR and LC‐MS analysis, SadA converted N‐succinyl l‐leucine into N‐succinyl l‐threo‐β‐hydroxyleucine with >99% diastereoselectivity. SadA is the first enzyme catalysing β‐hydroxylation of aliphatic amino acid‐related substances and a potent biocatalyst for the preparation of optically active β‐hydroxy amino acids.