Structural basis for methylesterase CheB regulation by a phosphorylation-activated domain

We report the x-ray crystal structure of the methylesterase CheB, a phosphorylation-activated response regulator involved in reversible modification of bacterial chemotaxis receptors. Methylesterase CheB and methyltransferase CheR modulate signaling output of the chemotaxis receptors by controlling the level of receptor methylation. The structure of CheB, which consists of an N-terminal regulatory domain and a C-terminal catalytic domain joined by a linker, was solved by molecular replacement methods using independent search models for the two domains. In unphosphorylated CheB, the N-terminal domain packs against the active site of the C-terminal domain and thus inhibits methylesterase activity by directly restricting access to the active site. We propose that phosphorylation of CheB induces a conformational change in the regulatory domain that disrupts the domain interface, resulting in a repositioning of the domains and allowing access to the active site. Structural similarity between the two companion receptor modification enzymes, CheB and CheR, suggests an evolutionary and/or functional relationship. Specifically, the phosphorylated N-terminal domain of CheB may facilitate interaction with the receptors, similar to the postulated role of the N-terminal domain of CheR. Examination of surfaces in the N-terminal regulatory domain of CheB suggests that despite a common fold throughout the response regulator family, surfaces used for protein–protein interactions differ significantly. Comparison between CheB and other response regulators indicates that analogous surfaces are used for different functions and conversely, similar functions are mediated by different molecular surfaces.     

Awareness of deficits during intracarotid anesthetic procedures in epilepsy: Comparisons of motor, naming, and comprehension awareness under amobarbital versus under etomidate

Awareness of deficits is often impaired following disruption of the right hemisphere. Intracarotid anesthetic procedures (IAPs) represent a unique method by which we can assess functioning of each hemisphere in isolation. We used this technique to explore deficits of awareness of specific functions-motor ability, naming, and comprehension-in patients with temporal lobe epilepsy. Some patients were injected with amobarbital, whereas others were injected with etomidate. We found that injection into the right hemisphere, or epileptogenic focus in the right hemisphere following injection in the left, resulted in the lowest levels of motor awareness. We also found a higher level of awareness for expressive language deficits and less awareness for receptive language deficits. Comparison of etomidate and amobarbital suggested more awareness following injection of etomidate. We discuss how these findings contribute to our understanding of the right hemisphere's special role in awareness, and how research in other disorders and in comparative neurology has shaped our conceptualization of the neuroanatomy of insight.     

Protective effects of fullerenol C60(OH)24 against doxorubicin-induced cardiotoxicity and hepatotoxicity in rats with colorectal cancer

The effects of fullerenol C₆₀(OH)₂₄ (Frl) at doses of 25, 50, and 100 mg/kg/week (for a time-span of 3 weeks) on heart and liver tissue after doxorubicin (Dox)-induced toxicity in rats with colorectal cancer were investigated. In the present study, we used an in vivo Wistar male rat model to explore whether Frl could protect against Dox-induced (1.5 mg/kg/week for 3 weeks) chronic cardio- and hepato- toxicity and compared the effect with a well-known antioxidant, vitamin C (100 mg/kg/week for 3 weeks). According to macroscopic, microscopic, hematological, biochemical, physiological, pharmacological, and pharmacokinetic results, we confirmed that, at all examined doses, Frl exhibits a protective influence on the heart and liver tissue against chronic toxicity induced by Dox.     

Possible interactions of genetic and immuno-neuro-endocrine regulatory mechanisms in pathogenesis of congenital anomalies

The process of organogenesis depends on genetic and environmental factors. Besides genetic background, congenital anomalies can also be influenced by micro environmental changes, which are related to maternal-foetal interactions followed by the production of cytokines, hormones, neurotransmitters, growth factors and biochemical mediators, and stress proteins. Pre-natal maternal stress, including infections, psychological stress and other teratogens, can influence a disregulation of maternal immune, endocrine and nervous systems, during pregnancy. This is a crucial condition for the abnormal growth and development of the foetus. Activated maternal immune system can alter the cytokine network and make it inadequate for normal embryogenesis and organogenesis. Heat-shock proteins play an important role in stress physiology repairing DNA errors or activating pro-inflammatory response. Regarded from this aspect, the altered cytokine network suggests aetiopathogenetic basis of congenital anomalies in neonates. It is our wish to point out our potentially harmful conditions in the development of congenital anomalies, as well as their control by using pre-natal and pre-conceptional diagnostics and treatment.     

In vivo evaluation of CYP2A6 and xanthine oxidase enzyme activities in the Serbian population

Purpose

The main aim of the study was to investigate the distribution of cytochrome P450 2A6 (CYP2A6) and xanthine oxidase (XO) enzyme activities in the Serbian population. Secondly, we tested the influence of genetics (CYP2A6 polymorphism), sex, and cigarette smoking on both enzymes.

Methods

One hundred forty healthy Serbian volunteers were genotyped for common CYP2A6 alleles. In 100 of them, CYP2A6 and XO activities were determined by the urinary 17U/17X and 1U/(1U?+?1X) ratios, respectively, after oral administration of 100 mg caffeine as a probe.

Results

A 21-fold variation in the 17U/17X ratio was observed (range: 0.49–10.28, mean?=?1.65, 95% CI: 1.49–1.83). The urinary 1U/(1U?+?1X) ratios displayed four-fold variation, ranging from 0.17 to 0.71 (mean?=?0.43, 95% CI: 0.41–0.45). CYP2A6 alleles *1A, *1B1, *9, *4 and *1B1x2 were found with frequencies of 0.579, 0.307, 0.082, 0.029, and 0.004 respectively. CYP2A6*5 was not detected. CYP2A6 genotype influenced interindividual variability in CYP2A6 enzyme activity (P?=?0.04). Cigarette smoking inhibited CYP2A6 enzyme activity (P?=?0.02), but had no effect on activity of XO (P?=?0.16).There was no significant difference between men and women in terms of CYP2A6 or XO activity.

Conclusions

Serbs displayed interindividual variations in CYP2A6 activity. CYP2A6 genotype and cigarette smoking, but not sex, influenced CYP2A6 enzyme activity. Unimodal distribution of XO enzyme activity in Serbs implies the absence of subjects with low enzyme activity in this population. XO activity is not influenced by sex or cigarette smoking.