Peptide-protein interaction markedly alters the functional properties of the catalytic subunit of aspartate transcarbamoylase.

Interaction of a 70-amino acid zinc-binding polypeptide from the regulatory chain of aspartate transcarbamoylase (ATCase) with the catalytic (C) subunit leads to dramatic changes in enzyme activity and affinity for ligand binding at the active sites. The complex between the polypeptide (zinc domain) and wild-type C trimer exhibits hyperbolic kinetics in contrast to the sigmoidal kinetics observed with the intact holoenzyme. Moreover, the Scatchard plot for binding N-(phosphonacetyl)-L-aspartate (PALA) to the complex is linear with a Kd corresponding to that evaluated for the holoenzyme converted to the relaxed (R) state. Additional evidence that the binding of the zinc domain to the C trimer converts it to the R state was attained with a mutant form of ATCase in which Lys 164 in the catalytic chain is replaced by Glu. As shown previously (Newell, J.O. & Schachman, H.K., 1990, Biophys. Chem. 37, 183-196), this mutant holoenzyme, which exists in the R conformation even in the absence of active site ligands, has a 50-fold greater affinity for PALA than the free C subunit. Adding the zinc domain to the C trimer containing the Lys 164-->Glu substitution leads to a 50-fold enhancement in the affinity for the bisubstrate analog yielding a value of Kd equal to that for the holoenzyme. A different mutant ATCase containing the Gln 231 to Ile replacement was shown (Peterson, C.B., Burman, D.L., & Schachman, H.K., 1992, Biochemistry 31, 8508-8515) to be much less active as a holoenzyme than as the free C trimer. For this mutant holoenzyme, the addition of substrates does not cause its conversion to the R state. However, the addition of the zinc domain to the Gln 231-->Ile C trimer leads to a marked increase in enzyme activity, and PALA binding data indicate that the complex resembles the R state of the holoenzyme. This interaction leading to a more active conformation serves as a model of intergenic complementation in which peptide binding to a protein causes a conformational correction at a site remote from the interacting surfaces resulting in activation of the protein. This linkage was also demonstrated by difference spectroscopy using a chromophore covalently bound at the active site, which served as a spectral probe for a local conformational change. The binding of ligands at the active sites was shown also to lead to a strengthening of the interaction between the zinc domain and the C trimer.     

广西、云南的PSEUDOSCHWAGERINA化石及其地层意义

该文记述了广西宜山马脑山剖面及云南八宝小独山剖面Pseudoschwaserina属34种(亚种),分析了两剖面Pseudoschwagerina动物群的面貌,讨论了Pseudoschwagerina的地层意义。研究表明,两剖面Pseudoschwagerina动物群具有地方性种稀少的共同特点,大多数种皆为广相型分子。从动物群的组成上看,广西、云南Pseudoschwagerina动物群与我国贵州、北美及俄罗斯等地的Pseudoschwagerina动物群有较大的相似性。但是,目前归入 Pseudoschwagerina名下的各种在形态上有着较大的差异,造成不同地区合Pseudoschwagerina地层带化石难以直接对比。根据对两剖面Pseudoschwagerina地层分布规律的研究以及国内、外Pseudochwagerina地理分布的资料,笔者建议选用 Pseudoschwagerina uddeni,P.beedei,P.robusta等 Pseudoschwagerina的典型分子做为含Pseudoschwagerina地层划分、对比的首要标准类群,选用P.uddeni和P.robusta分别做为确定Pseudoschwagerina带底、顶界线的首要标准种,以便于含Pseudoschwagerina地层的全球性的对比。     

隆德鱼的新材料及其系统关系的初步分析——辽宁西部晚中生代地层和鱼群研究之一

依据辽宁西部三个地点的新材料和宁夏、内蒙古的标本,对罗家峡隆德鱼(Longdeichthys luojiaxiaensis Liu,1982)的形态特征作了补充描述和修订,并初步分析讨论了“薄鳞鱼类”的研究现状以及隆德鱼的系统关系。认为隆德鱼可能已是鲱头鱼派(Clupeocephala)的成员,与德国和法国基末里期的Leptolepides sprattiformis(Blainville)最为相近。     

Regulation of estrogen receptor protein and messenger ribonucleic acid by estradiol and progesterone in rat uterus

The objective of this study was to examine the mechanisms of estrogen receptor (ER) processing and replenishment in the uterus of ovariectomized rats after estradiol and progesterone treatment. Uterine ER binding activity, ER protein and ER mRNA were measured by receptor binding exchange assay, Western blot and slot blot, respectively. The regulation of ER levels in rat uterus by estradiol and progesterone was very dramatic. Changes in ER protein were faithfully reflected by changes in binding activity. Estradiol caused receptor “processing” within 4 h of administration followed by recovery or “replenishment” of ER levels to the initial level by 20 h. The term “processing” has previously been used to describe the loss of ER binding activity in the early phase of estradiol-action, but it was never clear whether the ligand binding site was inactivated by processing or if the receptor molecule actually disappeared. This study shows that receptor “processing” constitutes disappearance of receptor protein and the later “replenishment” phase represents new ER protein rather than recycling of “processed” receptor. Progesterone-action, on the other hand, influenced only the “replenishment” phase by blocking recovery of ER protein. ER mRNA was suppressed by estradiol at 8 h, after the receptor was “processed” and “replenishment” already initiated. Progesterone, on the other hand, did not alter the steady state level of the message. Other mechanisms, such as regulation of translation rate of existing mRNA and changes in the rate of degradation of ER proteins are more likely involved in acute regulation of ER by these ovarian steroid hormones.     

Estimating tree-based dynamic treatment regimes using observational data with restricted treatment sequences

A dynamic treatment regime (DTR) is a sequence of decision rules that provide guidance on how to treat individuals based on their static and time-varying status. Existing observational data are often used to generate hypotheses about effective DTRs. A common challenge with observational data, however, is the need for analysts to consider “restrictions” on the treatment sequences. Such restrictions may be necessary for settings where (1) one or more treatment sequences that were offered to individuals when the data were collected are no longer considered viable in practice, (2) specific treatment sequences are no longer available, or (3) the scientific focus of the analysis concerns a specific type of treatment sequences (eg, “stepped-up” treatments). To address this challenge, we propose a restricted tree–based reinforcement learning (RT-RL) method that searches for an interpretable DTR with the maximum expected outcome, given a (set of) user-specified restriction(s), which specifies treatment options (at each stage) that ought not to be considered as part of the estimated tree-based DTR. In simulations, we evaluate the performance of RT-RL versus the standard approach of ignoring the partial data for individuals not following the (set of) restriction(s). The method is illustrated using an observational data set to estimate a two-stage stepped-up DTR for guiding the level of care placement for adolescents with substance use disorder.     

Rapid Analysis of Four Alkaloids in <i>Uncaria rhynchophylla</i> by Core-Shell Column HPLC and Quantitative Analysis of Multi-Components by Single Marker (QAMS)

As a traditional herbal medicine, the major alkaloids in Uncaria rhynchophylla have been proven to have blood pressure-lowering and sedative effects. It is essential to develop an effective method for the determination of the major alkaloids in U. rhynchophylla. In this research, a rapid quantitative analysis involving multi-components analysis by a single marker strategy coupled with core-shell column HPLC was adopted to analyse four alkaloids (corynoxeine, isocorynoxeine, isorhynchophylline, rhynchophylline) in U. rhynchophylla. Isorhynchophylline was selected as the internal reference substance, the content of which was determined by the traditional external standard method. Relative correction factors (RCF) between isorhynchophylline and the other three alkaloids were calculated respectively. The results showed that the QAMS method had good robustness under different HPLC instruments. Nineteen batches of U. rhynchophylla were tested. No significant difference was observed between the results by QAMS and EMS (Correlation coefficient > 0.99, p > 0.05). The QAMS method could be employed as a rapid, effective technique for the quality control of U. rhynchophylla.     

A Rapid Determination of 30 Prohibited Pesticide Residues in Lycii Fructus by UPLC-MS/MS

Prohibited pesticide residues have become one of the main factors affecting the quality and safety of Lycii Fructus, However, rarely studies focus on the rapid determination of these residues. Here, a total of 30 kinds of prohibited pesticide residues were determined by ultra-performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) in five different process ways. Pretreatment methods, chromatographic separation and detection conditions in mass spectrometry were all optimized accordingly. Among the five different pretreatment methods, the first and third solid phase extraction failed to provide high recoveries of sulfosulfuron compounds (both lower than 60%). Recovery of chlorphenamidine by the Quick Easy Cheap Effective Rugged and Safe multiresidue method (QuEChERS) was lower than 60%, which did not meet the requirements of trace determination. The concentrations of 30 prohibited pesticides residues treated by straightforward and solid phase extraction showed good linearity in their corresponding ranges, with correlation coefficients over 0.99. The average recoveries of straightforward ranged from 78.13% to 110.9%, while RSD ranged from 1.3% to 16.9%, albeit poor purification was observed. The recovery yield from solid phase extraction was between 67.75% and 103.08% with RSD value from 0.8% to 14.0%, which met the requirements of trace determination, this method has good precision and stability. These results could be employed to other Traditional Chinese Medicines (TCMs) in detecting prohibited pesticide residues.     

Comparative Transcriptome Analyses Reveal Genes Related to Spine Development in Cucumber (<i>Cucumis sativus</i>)

Fruit spine is an important quality trait of cucumber. To better understand the molecular basis of cucumber spine development and function, RNA-Seq was performed to identify differentially expressed genes (DEGs) in fruit spines of different development stages, namely, 8 days before anthesis (SpBA8), anthesis (SpA) and 8 days after anthesis (SpAA8). Stage-wise comparisons obtained 2,259 (SpBA8 vs. SpA), 4,551 (SpA vs. SpAA8), and 5,290 (SpBA8 vs. SpAA8) DEGs. All the DEGs were classified into eight expression clusters by trend analysis. Among these DEGs, in addition to the Mict, Tril, CsTTG1, CsMYB6, NS, and Tu genes that have been reported to regulate fruit spine formation, we found that the CsHDG11, CsSCL8, CsSPL8, CsZFP6 and CsZFP8 may also be involved in spine development in cucumber. Our study provides a theoretical basis for further research on molecular mechanisms of spine development in cucumber.     

Arbuscular Mycorrhizal Fungal Colonization at Different Succession Stages in Songnen Saline-Alkali Grassland

Arbuscular mycorrhizal (AM) fungi can form symbiosis with 90% of the vascular plants and play important roles in ecosystem. To realize the AM fungal colonization at different succession stages in saline-alkali land and screen AM fungi species with great functions, roots and soil samples were collected from the three succession stages of Songnen saline-alkali grassland. The soil properties and AM fungal colonization were measured, and the fungus distributed extensively in three stages was annotated by sequencing for AML1/AML2 target, subsequently, maize was selected as the host to verify its colonization. The results showed that the soil properties improved with the succession of saline-alkali grassland. The plants’ communities of the three stages could be colonized by AM fungi, and the colonization rate of Leymus chinensis (the third stage) ranged from 66.67% to 100%, Puccinellia tenuiflora (the second stage) ranged from 50% to 80%, while the Suaeda glauca (the first stage) was only 35%–60%. Glomeraceae sp1 was identified as the dominant AM fungi species which occurred frequently in the succession of saline-alkali land with the isolation frequency, relative abundance, and importance value of 100%, 18.1%, and 59.1%, respectively. The colonization rate of Glomeraceae sp1 in maize ranged from 80% to 87% and similar mycorrhizal characteristics were detected in the roots of P. tenuiflora, S. glauca, and L. chinensis, indicating that Glomeraceae sp1 colonized the samples in the field. The correlation matrix indicated that colonization rate, colonization intensity, and vesicle abundance were closely related to soil conditions most, and they were related significantly to all the soil properties except cellulase activity. Besides, redundancy analysis (RDA) showed that soil properties drove the changes of AM fungal colonization and sporulation. These results will provide theoretical support for realizing the relationship between AM fungal colonization and soil conditions, and also for the exploration of AM fungi species with great functions.

     

Sub-Cellular Distribution of Zinc in Different Vegetative Organs and Their Contribution to Grains Zinc Accumulation in Rice Under Different Nitrogen and Zinc Supply

Journal of Plant Growth Regulation - Zinc is an important micronutrient for the growth and development of human body and plants. Proper use of nitrogen fertilizer and foliar application of Zn have...