Interaction of the Neurospora crassa heat shock factor with the heat shock element during heat shock and different developmental stages

The interaction of the heat shock factor (HSF) with the heat shock element (HSE) was determined by a non-radioactive electrophoretic mobility shift assay, in order to analyze HSF regulation in Neurospora crassa. HSF binds to HSE under normal, non-stress conditions and is thus constitutively trimerized. Upon heat shock, the HSF-HSE complex shows a retarded mobility. This was also observed in Saccharomyces cerevisiae, where this mobility shift was shown to be due to HSF phosphorylation [Sorger and Pelham (1988) Cell 54, 855-864]. In N. crassa, HSE-dependent electrophoretic mobility shift is temperature- and time-dependent. Under normal growth conditions, the HSF is located in the cytoplasm as well as in the nucleus. In germinating conidia the HSF shows a retarded mobility typical for heat shock even at normal growth temperatures. No HSF-dependent mobility shift was detectable in aerial hyphae.     

The ChrA homologue from a sulfur-regulated gene cluster in cyanobacterial plasmid pANL confers chromate resistance

The cyanobacterium Synechococcus elongatus strain PCC 7942 possesses pANL, a plasmid rich in genes related to sulfur metabolism. One of these genes, srpC, encodes the SrpC protein, a homologue of the CHR chromate ion transporter superfamily. The srpC gene was cloned and expressed in Escherichia coli and its role in relation to sulfate and chromate was analyzed. srpC was unable to complement the growth of an E. coli cysA sulfate uptake mutant when sulfate was utilized as a sole sulfur source, suggesting that SrpC is not a sulfate transporter. Expression of srpC in E. coli conferred chromate resistance and caused diminished chromate uptake. These results suggest that the S. elongatus SrpC protein functions as a transporter that extrudes chromate ions from the cell’s cytoplasm, and further demonstrate the close relationship between sulfate and chromate metabolism in this organism.     

Switch or funnel: how RND-type transport systems control periplasmic metal homeostasis

Bacteria have evolved several transport mechanisms to maintain metal homeostasis and to detoxify the cell. One mechanism involves an RND (resistance-nodulation-cell division protein family)-driven tripartite protein complex to extrude a variety of toxic substrates to the extracellular milieu. These efflux systems are comprised of a central RND proton-substrate antiporter, a membrane fusion protein, and an outer membrane factor. The mechanism of substrate binding and subsequent efflux has yet to be elucidated. However, the resolution of recent protein crystal structures and genetic analyses of the components of the heavy-metal efflux family of RND proteins have allowed the developments of proposals for a substrate transport pathway. Here two models of substrate extrusion through RND protein complexes of the heavy-metal efflux protein family are described. The funnel model involves the shuttling of periplasmic substrate from the membrane fusion protein to the RND transporter and further on through the outer membrane factor to the extracellular space. Conversely, the switch model requires substrate binding to the membrane fusion protein, inducing a conformational change and creating an open-access state of the tripartite protein complex. The extrusion of periplasmic substrate bypasses the membrane fusion protein, enters the RND-transporter directly via its substrate-binding site, and is ultimately eliminated through the outer membrane channel. Evidence for and against the two models is described, and we propose that current data favor the switch model.     

Pulmonary hypertension complicating pulmonary sarcoidosis

Pulmonary hypertension (PH) is a severe complication of sarcoidosis, with an unknown prevalence. The aetiology is multifactorial, and the exact mechanism of PH in the individual patient is often difficult to establish. The diagnostic work-up and treatment of PH in sarcoidosis is complex, and should therefore be determined by a multidisciplinary expert team in a specialised centre. It is still a major challenge to identify sarcoidosis patients at risk for developing PH. There is no validated algorithm when to refer a patient suspected for PH, and PH analysis itself is difficult. Until present, there is no established therapy for PH in sarcoidosis. Besides optimal treatment for sarcoidosis, case series evaluating new therapeutic options involving PH-targeted therapy are arising for a subgroup of patients. This review summarises the current knowledge regarding the aetiology, diagnosis and possible treatment options for PH in sarcoidosis.     

实验动物皮肤病原真菌检测方法的改良

目的对实验动物皮肤病原真菌2种培养方法进行了比较。方法将采集到的3只皮肤真菌感染病兔样品经由沙氏平皿法和沙氏试管斜面培养法分别进行培养。结果在3只真菌感染病兔中应用试管斜面法我们只检测到1例皮肤病原真菌阳性,而采用沙氏平皿法3例阳性全部检出。结论结合临床检测经验,我们认为本研究的沙氏平皿法优于沙氏试管斜面法,在实验动物皮肤病原真菌常规检测中具有推广应用价值。     

Zur circadianen Rhythmik des Sauerstoffverbrauches von Drosophila

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