Extracellular secretion of levansucrase from Zymomonas mobilis in Escherichia coli

Secretion of levansucrase from Zymomonas mobilis in Escherichiacoli by glycine supplement was investigated. A significant amount of levansucrase (about 25% of total activity) was found in intact whole-cells. Cell fractionation experiments showed that levansucrase was found both in the periplasmic space and in the cytoplasmic fraction of E. coli. None or only trace amounts of levansucrase was detected in the extracellular culture broth at 24 h of cultivation and it accrued with the increasing concentration of glycine in the culture medium and duration of the culture period. Optimal glycine concentration for the maximum secretion of levansucrase was in the range of 0.8-1%, in which approximately 20-50% of levansucrase was released into the extracellular fraction at 24 h of cultivation, although glycine retarded the bacterial growth.     

The use of tryptophan mutants in identifying the 296 nm transient absorbing species during the photocycle of bacteriorhodopsin

The transient absorption at 296 nm was part of the spectroscopic evidence that initiated the proposal that tyrosinate (Tyr-) is formed during, and important to, the photocycle of bacteriorhodopsin (bR). Recent evidence against such a proposal comes from the results of NMR, UV Raman as well as electron cryo-microscopic structural studies. This makes it credible to assign this absorption to a charge perturbation of the lowest energy absorption of one of the tryptophan (Trp) residues in bR. The transient absorption at 296 nm is examined for each of 8 tryptophan mutants in which Trp is substituted by phenylalanine or cysteine, which absorb at shorter wavelength. It is shown that while all go through the photocycle, all but Trp-182 mutant show this transient absorption. This strongly suggests the assignment of this absorption to a charge perturbaton of the lowest energy absorption of Trp-182 during the photocycle. The chemical identity of the perturbing charge(s) is briefly discussed.     

Draft Genome Sequence of Escherichia coli W26, an Enteric Strain Isolated from Cow Feces

An enteric bacterium, Escherichia coli W26 (KACC 16630), was isolated from feces from a healthy cow in South Korea. Here, we report the draft genome sequence of the isolate, which is closely affiliated with commensal strains belonging to E. coli phylogroup B1.     

MRI Features in a Canine Model of Ischemic Stroke: Correlation between Lesion Volume and Neurobehavioral Status during the Subacute Stage

The purpose of this study was to evaluate the diagnostic value of magnetic resonance imaging (MRI) and assess the correlation between the volume of the ischemic lesion and neurobehavioral status during the subacute stage of ischemic stroke. Ischemic stroke was induced in 6 healthy laboratory beagles through permanent occlusion of the middle cerebral artery (MCAO). T2-weighted and fluid-attenuated inversion recovery (FLAIR) imaging, diffusion-weighted imaging (DWI), measurement of the apparent diffusion coefficient (ADC) ratio, and neurobehavioral evaluation were performed 3 times serially by using a 1.5-T MR system: before and 3 and 10 d after MCAO. Ischemic lesions demonstrated T2 hyperintensity, FLAIR hyperintensity, and DWI hyperintensity. The ADC ratio was decreased initially but then was increased at 10 d after MCAO. Ischemic lesion volumes on T2-weighted and FLAIR imaging were not significantly different from those on DWI. The lesion volume and neurobehavioral score showed strong correlation. Our results suggest that conventional MRI may be a reliable diagnostic tool during the subacute stage of canine ischemic stroke.Abbreviations: ADC, apparent diffusion coefficient; DWI, diffusion-weighted imaging; FLAIR, fluid-attenuated inversion recovery; MCAO, middle cerebral artery occlusion; MRI, magnetic resonance imaging; PWI, perfusion-weighted imagingIn human medicine, stroke is a leading cause of adult mortality and neurologic disability worldwide.¹ Strokes previously were thought to be uncommon in small animals, but the true prevalence is unknown.⁴ These events are now recognized more frequently in dogs because of increased use of magnetic resonance imaging (MRI).^5,14,17Because the infusion of thrombolytic agents, such as urokinase or tissue plasminogen activator, within 3 to 6 h of the onset symptoms is effective in restoring blood flow and improving stroke outcome in humans,¹⁹ the detection of early ischemic changes is now thought to be necessary to improve patient outcome. Computed tomography and conventional MRI are not sufficiently sensitive to predict the presence and extent of ischemic damage during the acute stage after a stroke.^12,20 Therefore several MRI sequences, such as fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), and MR angiography, have been developed for early diagnosis and subsequent follow-up of ischemic stroke.³ High-field magnetic strengths (at least 1.5 T) are necessary to perform these sequences.In contrast to the situation in humans, ischemic stroke in many dogs is diagnosed during the subacute stage—24 h to 6 wk after the vascular insult—due to the time lag between the onset of clinical signs to referral and to the lack of standard diagnostic protocols for ischemic stroke in dogs. In most reports of strokes in dogs, the median interval between the onset of neurologic dysfunction and performance of an MRI was more than 2 d.^5,14,17 Whereas DWI has marked sensitivity to very early ischemic changes in the brain, T2-weighted and FLAIR images gradually become more hyperintense later (that is, during the first 24 h after the insult).³ Therefore, hyperintensity on T2-weighted and FLAIR images is believed to be representative of mature lesions.¹⁵ In light of these findings, we hypothesized that conventional MR sequences, such as T2-weighted and FLAIR imaging as well as DWI would be used for the diagnosis of the subacute stage of ischemic stroke in dogs.The purpose of this study was to evaluate the diagnostic value of MRI and assess the correlation between the volume of ischemic lesions and neurobehavioral status during the subacute stage of ischemic stroke in dogs. We therefore investigated the lesion volume of T2-weighted and FLAIR images compared with that on DWI images. Furthermore, we assessed the relationship between the apparent diffusion coefficient (ADC) of the ischemic lesions and the neurobehavioral status of the dogs.     

Inhibitory role of RhoA on senescence-like growth arrest by a mechanism involving modulation of phosphatase activity

Recently, negative effects of phosphatase in tumorigenesis and metastasis have been suggested in various tumor types. In this study, we showed that RhoA activation modulated phosphatase during senescence-like arrest in human prostate cancer cells. Under senescence-inducing condition, decreased Erk phosphorylation was detected in caRhoA-transfected cells and inactivation of Erk, but not p38, prevented doxorubicin-induced cell senescence. Cells were induced to senescence by inhibition of phosphatase activity (VHR, MKP3, or PP2A) without additional cellular stress. Of interest, caRhoA prevented doxorubicin-induced decrease of phosphatase. Thus, we postulate that RhoA signaling may protect cells against cellular senescence by maintaining phosphatase activity and Erk dephosphorylation.     

Genome-wide analysis and stress-responsive expression of CCCH zinc finger family genes in <Emphasis Type="Italic">Brassica rapa</Emphasis>

Background

Ubiquitous CCCH nucleic acid-binding motif is found in a wide-variety of organisms. CCCH genes are involved in plant developmental processes and biotic and abiotic stress responses. Brassica rapa is a vital economic crop and classical model plant of polyploidy evolution, but the functions of CCCH genes in B. rapa are unclear.

Results

In this study, 103 CCCH genes in B. rapa were identified. A comparative analysis of the chromosomal position, gene structure, domain organization and duplication event between B. rapa and Arabidopsis thaliana were performed. Results showed that CCCH genes could be divided into 18 subfamilies, and segmental duplication might mainly contribute to this family expansion. C-X_7/8-C-X₅-C₃-H was the most commonly found motif, but some novel CCCH motifs were also found, along with some loses of typical CCCH motifs widespread in other plant species. The multifarious gene structures and domain organizations implicated functional diversity of CCCH genes in B. rapa. Evidence also suggested functional redundancy in at least one subfamily due to high conservation between members. Finally, the expression profiles of subfamily-IX genes indicated that they are likely involved in various stress responses.

Conclusion

This study provides the first genome-wide characterization of the CCCH genes in B. rapa. The results suggest that B. rapa CCCH genes are likely functionally divergent, but mostly involved in plant development and stress response. These results are expected to facilitate future functional characterization of this potential RNA-binding protein family in Brassica crops.