Out-of-hospital cardiac arrest at place of residence is associated with worse outcomes in patients admitted to intensive care : a post-hoc analysis of the Targeted Temperature Management trial

BACKGROUND: The majority of out-of-hospital cardiac arrests (OHCAs) occur at place residence, which is associated with worse outcomes in unselected prehospital populations. Our aim was to investigate whether location of arrest was associated with outcome in a selected group of initial survivors admitted to intensive care.METHODS: This is a post-hoc analysis of the Targeted Temperature Management after cardiac arrest trial (TTM trial), a multicenter controlled trial, randomizing 950 OHCA patients to an intervention of 33°C or 36°C. The location of cardiac arrest was defined as place of residence vs. public place or other. The outcome measures were mortality and neurological outcome, as defined by the Cerebral Performance Category scale, at 180 days.RESULTS: Approximately half of 938 included patients arrested at place of residence (53%). Location groups did not differ with respect to age (p=0.11) or witnessed arrests (p=0.48) but bystander CPR was less common (p=0.02) at place of residence. OHCA at place of residence was associated with higher 180-day mortality, 55% vs. 38% (p<0.001) and worse neurological outcome, 61% vs. 43% (p<0.001) compared with a public place or other. After adjusting for known confounders, OHCA at place of residence remained an independent predictor of mortality (p=0.007).CONCLUSIONS: Half of all initial survivors after OHCA admitted to intensive care had an at place of residence which was independently associated with poor outcomes. Actions improve outcomes after OHCA at place of residence should be addressed in future trials

Thioredoxin A Active-Site Mutants Form Mixed Disulfide Dimers That Resemble Enzyme–Substrate Reaction Intermediates

Thioredoxin functions in nearly all organisms as the major thiol–disulfide oxidoreductase within the cytosol. Its prime purpose is to maintain cysteine-containing proteins in the reduced state by converting intramolecular disulfide bonds into dithiols in a disulfide exchange reaction. Thioredoxin has been reported to contribute to a wide variety of physiological functions by interacting with specific sets of substrates in different cell types. To investigate the function of the essential thioredoxin A (TrxA) in the low-GC Gram-positive bacterium Bacillus subtilis, we purified wild-type TrxA and three mutant TrxA proteins that lack either one or both of the two cysteine residues in the CxxC active site. The pure proteins were used for substrate-binding studies known as “mixed disulfide fishing” in which covalent disulfide-bonded reaction intermediates can be visualized. An unprecedented finding is that both active-site cysteine residues can form mixed disulfides with substrate proteins when the other active-site cysteine is absent, but only the N-terminal active-site cysteine forms stable interactions. A second novelty is that both single-cysteine mutant TrxA proteins form stable homodimers due to thiol oxidation of the remaining active-site cysteine residue. To investigate whether these dimers resemble mixed enzyme–substrate disulfides, the structure of the most abundant dimer, C32S, was characterized by X-ray crystallography. This yielded a high-resolution (1.5Å) X-ray crystallographic structure of a thioredoxin homodimer from a low-GC Gram-positive bacterium. The C32S TrxA dimer can be regarded as a mixed disulfide reaction intermediate of thioredoxin, which reveals the diversity of thioredoxin/substrate-binding modes

Proteins evolve on the edge of supramolecular self-assembly

The self-association of proteins into symmetric complexes is ubiquitous in all kingdoms of life1,2,3,4,5,6. Symmetric complexes possess unique geometric and functional properties, but their internal symmetry can pose a risk. In sickle-cell disease, the symmetry of haemoglobin exacerbates the effect of a mutation, triggering assembly into harmful fibrils7. Here we examine the universality of this mechanism and its relation to protein structure geometry. We introduced point mutations solely designed to increase surface hydrophobicity among 12 distinct symmetric complexes from Escherichia coli. Notably, all responded by forming supramolecular assemblies in vitro, as well as in vivo upon heterologous expression in Saccharomyces cerevisiae. Remarkably, in four cases, micrometre-long fibrils formed in vivo in response to a single point mutation. Biophysical measurements and electron microscopy revealed that mutants self-assembled in their folded states and so were not amyloid-like. Structural examination of 73 mutants identified supramolecular assembly hot spots predictable by geometry. A subsequent structural analysis of 7,471 symmetric complexes showed that geometric hot spots were buffered chemically by hydrophilic residues, suggesting a mechanism preventing mis-assembly of these regions. Thus, point mutations can frequently trigger folded proteins to self-assemble into higher-order structures. This potential is counterbalanced by negative selection and can be exploited to design nanomaterials in living cells.</p