The Examined Life

Two prisoners languish in adjacent cells, wishing to communicate with each other. They learn that the most effective way of doing so is by exchanging taps on the wall that divides their cells. The prisoners connect through the very partition that separates them. In this way, the philosopher Simone Weil writes of her thought experiment, “every separation is a link” (1952, p. 132).

FAD binding, cobinamide binding and active site communication in the corrin reductase (CobR)

Adenosylcobalamin, the coenzyme form of vitamin B12, is one Nature's most complex coenzyme whose de novo biogenesis proceeds along either an anaerobic or aerobic metabolic pathway. The aerobic synthesis involves reduction of the centrally chelated cobalt metal ion of the corrin ring from Co(II) to Co(I) before adenosylation can take place. A corrin reductase (CobR) enzyme has been identified as the likely agent to catalyse this reduction of the metal ion. Herein, we reveal how Brucella melitensis CobR binds its coenzyme FAD (flavin dinucleotide) and we also show that the enzyme can bind a corrin substrate consistent with its role in reduction of the cobalt of the corrin ring. Stopped-flow kinetics and EPR reveal a mechanistic asymmetry in CobR dimer that provides a potential link between the two electron reduction by NADH to the single electron reduction of Co(II) to Co(I)

A blood atlas of COVID-19 defines hallmarks of disease severity and specificity.

Treatment of severe COVID-19 is currently limited by clinical heterogeneity and incomplete description of specific immune biomarkers. We present here a comprehensive multi-omic blood atlas for patients with varying COVID-19 severity in an integrated comparison with influenza and sepsis patients versus healthy volunteers. We identify immune signatures and correlates of host response. Hallmarks of disease severity involved cells, their inflammatory mediators and networks, including progenitor cells and specific myeloid and lymphocyte subsets, features of the immune repertoire, acute phase response, metabolism, and coagulation. Persisting immune activation involving AP-1/p38MAPK was a specific feature of COVID-19. The plasma proteome enabled sub-phenotyping into patient clusters, predictive of severity and outcome. Systems-based integrative analyses including tensor and matrix decomposition of all modalities revealed feature groupings linked with severity and specificity compared to influenza and sepsis. Our approach and blood atlas will support future drug development, clinical trial design, and personalized medicine approaches for COVID-19

Cognition and Embodiment: Investigating the expert memory in musical and theatrical performance

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Embodiment, Emotion and Expertise: The experience of musical performance for the expert musician

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Seeing yellow : 'connection' and routine in professional musicians' experience of music performance

What is it like for a professional musician to perform music in front of a live audience? We use Strauss and Corbin’s (1998) Grounded Theory to conduct qualitative research with 10 professional musicians to investigate their experience of music performance. We find performance to extend temporally beyond time spent before an audience and to include performers’ rituals of separation from everyday life. Using the abridged version of the model emerging from this data that we present in this article, we investigate how professional musicians’ experience of music performance centers on forging ‘connection’ with an audience and the ways in which this process is facilitated by the pre- and post-performance routines in which musicians engage. We find musicians’ understandings and experiences of ‘connection’ during performance to differ greatly, being influenced by their positioning on two spectra that emerge in this study and indicate the extent to which, during performance, musicians: a) value attentiveness and/or attunement in an audience and b) are open to variability.19 page(s

Myosin cleft closure determines the energetics of the actomyosin interaction

Formation of the strong binding interaction between actin and myosin is essential for force generation in muscle and in cytoskeletal motor systems. To clarify the role of the closure of myosin's actin-binding cleft in the actomyosin interaction, we performed rapid kinetic, spectroscopic, and calorimetric experiments and atomic-level energetic calculations on a variety of myosin isoforms for which atomic structures are available. Surprisingly, we found that the endothermic actin-binding profile of vertebrate skeletal muscle myosin subfragment-1 is unique among studied myosins. We show that the diverse propensity of myosins for cleft closure determines different energetic profiles as well as structural and kinetic pathways of actin binding. Depending on the type of myosin, strong actin binding may occur via induced-fit or conformational preselection mechanisms. However, cleft closure does not directly determine the kinetics and affinity of actin binding. We also show that cleft closure is enthalpically unfavorable, reflecting the development of an internal strain within myosin in order to adopt precise steric complementarity to the actin filament. We propose that cleft closure leads to an increase in the torsional strain of myosin's central β-sheet that has been proposed to serve as an allosteric energy-transducing spring during force generation.—Takács, B., O'Neall-Hennessey, E., Hetényi, C., Kardos, J., Szent-Györgyi, A. G., Kovács, M. Myosin cleft closure determines the energetics of the actomyosin interaction

Insight into the molecular mechanism of the multitasking kinesin-8 motor

Members of the kinesin-8 motor class have the remarkable ability to both walk towards microtubule plus-ends and depolymerise these ends on arrival, thereby regulating microtubule length. To analyse how kinesin-8 multitasks, we studied the structure and function of the kinesin-8 motor domain. We determined the first crystal structure of a kinesin-8 and used cryo-electron microscopy to calculate the structure of the microtubule-bound motor. Microtubule-bound kinesin-8 reveals a new conformation compared with the crystal structure, including a bent conformation of the α4 relay helix and ordering of functionally important loops. The kinesin-8 motor domain does not depolymerise stabilised microtubules with ATP but does form tubulin rings in the presence of a non-hydrolysable ATP analogue. This shows that, by collaborating, kinesin-8 motor domain molecules can release tubulin from microtubules, and that they have a similar mechanical effect on microtubule ends as kinesin-13, which enables depolymerisation. Our data reveal aspects of the molecular mechanism of kinesin-8 motors that contribute to their unique dual motile and depolymerising functions, which are adapted to control microtubule length