RESUMO
Phytochromes are red-light photoreceptors that were first characterized in plants, with homologs in photosynthetic and non-photosynthetic bacteria known as bacteriophytochromes (BphPs). Upon absorption of light, BphPs interconvert between two states denoted Pr and Pfr with distinct absorption spectra in the red and far-red. They have recently been engineered as enzymatic photoswitches for fluorescent-marker applications in non-invasive tissue imaging of mammals. This article presents cryo- and room-temperature crystal structures of the unusual phytochrome from the non-photosynthetic myxo-bacterium Stigmatella aurantiaca (SaBphP1) and reveals its role in the fruiting-body formation of this photomorphogenic bacterium. SaBphP1 lacks a conserved histidine (His) in the chromophore-binding domain that stabilizes the Pr state in the classical BphPs. Instead it contains a threonine (Thr), a feature that is restricted to several myxobacterial phytochromes and is not evolutionarily understood. SaBphP1 structures of the chromophore binding domain (CBD) and the complete photosensory core module (PCM) in wild-type and Thr-to-His mutant forms reveal details of the molecular mechanism of the Pr/Pfr transition associated with the physiological response of this myxobacterium to red light. Specifically, key structural differences in the CBD and PCM between the wild-type and the Thr-to-His mutant involve essential chromophore contacts with proximal amino acids, and point to how the photosignal is transduced through the rest of the protein, impacting the essential enzymatic activity in the photomorphogenic response of this myxobacterium.
RESUMO
GOALS OF WORK: Increasing economical and administrative constraints and changes in health-care systems constitute a risk for burnout, especially for cancer physicians. However, little is known about differences across medical specialties and the importance of work characteristics. METHODS: A postal questionnaire addressing burnout, psychiatric morbidity, sociodemographics and work characteristics was administered to 180 cancer physicians, 184 paediatricians and 197 general practitioners in Switzerland. RESULTS: A total of 371 (66%) physicians participated in the survey. Overall, one third of the respondents expressed signs indicative of psychiatric morbidity and of burnout, including high levels of emotional exhaustion (33%) and depersonalisation/cynicism (28%) and a reduced feeling of personal accomplishment (20%). Workload (>50 h/week), lack of continuing education (<6 h/month) and working in a public institution were significantly associated with an increased risk of burnout. After adjustment for these characteristics, general practitioners had a higher risk for emotional exhaustion (OR: 2.0, 95% CI: 1.1 to 3.6) and depersonalisation (OR: 2.7, 95% CI: 1.4 to 5.3). CONCLUSION: In this Swiss sample, cancer clinicians had a significant lower risk of burnout, despite a more important workload. Among possible explanations, involvement in research and teaching activities and access to continuing education may have protected them.
