Distinct functions of two FabA-like dehydratase domains of polyunsaturated fatty acid synthase in the biosynthesis of very long-chain polyunsaturated fatty acids

Thraustochytrium is a unicellular marine protist for the commercial production of very long-chain polyunsaturated fatty acids (VLCPUFAs). Biosynthesis of these VLCPUFAs in the protist is catalysed by a PUFA synthase comprising three subunits, each with multiple catalytic domains. Among these domains, two tandem FabA-like dehydratase domains (DH1 and DH2) in subunit-C together are responsible for introducing double bonds in VLCPUFAs. Domain swapping analysis in yeast showed that the defective phenotype of a Scfas1 mutant could be complemented by expressing an engineered ScFAS1 gene in which the DH domain was replaced by a single DH1 or mutated DH2 of the two. Heterologous expression of the PUFA synthase in E. coli showed that the mutation of DH1 of the two or deletion of DH1 or substitution of DH1 with DH2 resulted in the complete loss of activity in the biosynthesis of VLCPUFAs. Mutation of DH2 of the two or deletion of the DH2 domain produced a small amount of DPA, but not docosahexaenoic acid (DHA). These results indicate that each of the two FabA-like domains of the PUFA synthase possesses distinct function. DH1 domain is essential for the biosynthesis of VLCPUFAs, but DH2 domain is required for the biosynthesis of DHA.     

Study on the Effect of Kidney Transplantation on the Health of the Patients’ Offspring: A Report on 252 Chinese Children

Even though the incidence of pregnancies in the female recipients is lower and also chronic renal disease in male patients is associated with impaired spermatogenesis, the health of the children born to these patients was not studied. In this report, we discuss information on the growth and development of offspring of 248 male and female kidney recipient patients. Physical and routine clinical measurements of the 252 offspring (129 male and 123 female) born to these transplantation patients were made along with the intelligence tests. In some of these children chest X-ray and immune indices were assessed. Among the recipients, 219 males fathered 223 children with an average birth weight of 3,255 ± 374 g and 29 female recipients gave birth to 29 children with an average birth weight of 2,923 ± 551. While most of these children were normal, we noticed a case of soft double toe, a case of short tongue tie, five cases of marginal mental retardation, three cases of proteinuria, six cases of microscopic hematuria, 15 cases of low hemoglobin, and 21 cases with recurrent respiratory tract infections. We conclude that kidney transplantation has no significant impact on the growth, development, health, and intelligence of the offspring born to recipients.     

Population Differences in Brain Morphology and Microstructure among Chinese,Malay, and Indian Neonates

We studied a sample of 75 Chinese, 73 Malay, and 29 Indian healthy neonates taking part in a cohort study to examine potential differences in neonatal brain morphology and white matter microstructure as a function of ethnicity using both structural T2-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). We first examined the differences in global size and morphology of the brain among the three groups. We then constructed the T2-weighted MRI and DTI atlases and employed voxel-based analysis to investigate ethnic differences in morphological shape of the brain from the T2-weighted MRI, and white matter microstructure measured by fractional anisotropy derived from DTI. Compared with Malay neonates, the brains of Indian neonates’ tended to be more elongated in anterior and posterior axis relative to the superior-inferior axis of the brain even though the total brain volume was similar among the three groups. Although most anatomical regions of the brain were similar among Chinese, Malay, and Indian neonates, there were anatomical variations in the spinal-cerebellar and cortical-striatal-thalamic neural circuits among the three populations. The population-related brain regions highlighted in our study are key anatomical substrates associated with sensorimotor functions.     

Structures of Sarcorucinine D and Pachyaximine A,B

In this paper, three new alkaloids, sarcorucinine D (1), and paehyaximine A, B (2, 3) were isolated from Sarcococca ruscifolia Stapf and Pachysandra axillaris Franch, respectively. The structures of sarcorucinine D (1) and pachyaximine A, B (2, 3) were elucidated to be 3β-hydroxyl-20α-dimethylamino-5α-pregnane (1); and 3β-methoxyl-20α-dimethylamino-pregne-5-ne (2); and 3β-methoxyl-16-hydroxyl-20α-dimethylaminopregne-5-ne (16-hydroxyl-pachyaxi- mine A) (3), respectively.     

DIFFERENT PHYSIOLOGICAL RESPONSES OF FOUR MARINE SYNECHOCOCCUS STRAINS (CYANOPHYCEAE) TO NICKEL STARVATION UNDER IRON‐REPLETE AND IRON‐DEPLETE CONDITIONS1

Synechococcus species are important primary producers in coastal and open‐ocean ecosystems. When nitrate was provided as the sole nitrogen source, nickel starvation inhibited the growth of strains WH8102 and WH7803, while it had little effect on two euryhaline strains, WH5701 and PCC 7002. Nickel was required for the acclimation of Synechococcus WH7803 to low iron and high light. In WH8102 and WH7803, nickel starvation decreased the linear electron transport activity, slowed down Q_A reoxidation, but increased the connectivity factor between individual photosynthetic units. Under such conditions, the reduction of their intersystem electron transport chains was expected to increase, and their cyclic electron transport around PSI would be favored. Nickel starvation decreased the total superoxide dismutase (SOD) activity of WH8102 and WH7803 by 30% and 15% of the control, respectively. The protein‐bound ⁶³Ni of the oceanic strain WH8102 comigrated with SOD activity on nondenaturing gels and thus provided additional evidence for the existence of active NiSOD in Synechococcus WH8102. In WH7803, it seems likely that nickel starvation affected other metabolic pathways and thus indirectly affected the total SOD activity.     

Biochemical and mutagenic analysis of I-CreII reveals distinct but important roles for both the H-N-H and GIY-YIG motifs

Homing endonucleases typically contain one of four conserved catalytic motifs, and other elements that confer tight DNA binding. I-CreII, which catalyzes homing of the Cr.psbA4 intron, is unusual in containing two potential catalytic motifs, H-N-H and GIY-YIG. Previously, we showed that cleavage by I-CreII leaves ends (2-nt 3′ overhangs) that are characteristic of GIY-YIG endonucleases, yet it has a relaxed metal requirement like H-N-H enzymes. Here we show that I-CreII can bind DNA without an added metal ion, and that it binds as a monomer, akin to GIY-YIG enzymes. Moreover, cleavage of supercoiled DNA, and estimates of strand-specific cleavage rates, suggest that I-CreII uses a sequential cleavage mechanism. Alanine substitution of a number of residues in the GIY-YIG motif, however, did not block cleavage activity, although DNA binding was substantially reduced in several variants. Substitution of conserved histidines in the H-N-H motif resulted in variants that did not promote DNA cleavage, but retained high-affinity DNA binding—thus identifying it as the catalytic motif. Unlike the non-specific H-N-H colicins, however; substitution of the conserved asparagine substantially reduced DNA binding (though not the ability to promote cleavage). These results indicate that, in I-CreII, two catalytic motifs have evolved to play important roles in specific DNA binding. The data also indicate that only the H-N-H motif has retained catalytic ability.     

Ethanol disrupts the formation of hypochord and dorsal aorta during the development of embryonic zebrafish

It has been demonstrated that maternal drinking during pregnancy had serious adverse effects on the health of the newborns. Fetal alcohol syndrome (FAS) is the most important developmental abnormality caused by maternal alcohol abuse during pregnancy. Clinically, it is characterized by head and facial ab-normalities, cardiovascular malformation, and perma-nent nervous system damage[1,2]. A lot of experimental models have been developed to study the ethanol’s effects on embryonic development,…     

Structure of the hirulog 3-thrombin complex and nature of the S' subsites of substrates and inhibitors.

The X-ray crystallographic structure of the human alpha-thrombin complex with hirulog 3 (a potent, noncleavable hirudin-based peptide of the "hirulog" class containing a beta-homoarginine at the scissile bond), which is isomorphous with that of the hirugen-thrombin crystal structure, was solved at 2.3-A resolution by starting with a model for thrombin derived from the hirugen-thrombin complex and was refined by restrained least squares methods (R = 0.132). Residues of hirulog 3 were well-defined in the electron density, which included most of the pentaglycine linker and the C-terminal helical turn that was disordered in a related structure of thrombin with hirulog 1. The interactions of D-Phe1'-Pro2'-beta-homoArg3' with the active site of thrombin were essentially identical to those of related structures of PPACK- (D-Phe-Pro-Arg chloromethyl ketone) and hirulog 1-thrombin, with the guanidinium function of the arginyl P1 residue forming a hydrogen-bonding ion pair with Asp189 of the S1 site. A noticeable shift in the CA atom of beta-homoArg3' due to the methylene insertion displaces the scissile bond from attack by Ser195, thus imparting proteolytic stability to the beta-homoArg hirulog derivative. Resolution of the pentaglycine spacer, linking N- and C-terminal functional domains into a single oligopeptide bivalent inhibitor, permitted delineation of corresponding S' subsites of thrombin. The position of Gly4' (P1') is stabilized by three hydrogen bonds with His57, Lys60F, and Ser195, while the conformational angles maintained in a strained, nonallowed configuration for non-glycyl amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Simultaneous determination of five characteristic stilbene glycosides in root bark of Morus albus L. (Cortex Mori) using high-performance liquid chromatography

Introduction – Cortex Mori, one of the well‐known traditional Chinese herbal medicines, is derived from the root bark of Morus alba L. according to the China Pharmacopeia. Stilbene glycosides are the main components isolated from aqueous extracts of Morus alba and their content varies depending on where Cortex Mori was collected. We have established a qualitative and quantitative method based on the bioactive stilbene glycosides for control of the quality of Cortex Mori from different sources. Objective – To develop a high‐performance liquid chromatography coupled with ultraviolet absorption detection for simultaneous quantitative determination of five major characteristic stilbene glycosides in 34 samples of the root bark of Morus alba L. (Cortex Mori) from different sources. Methodology – The analysis was performed on an ODS column using methanol‐water‐acetic acid (18: 82: 0.1, v/v/v) as the mobile phase and the peaks were monitored at 320 nm. Results – All calibration curves showed good linearity (r ≥ 0.9991) within test ranges. This method showed good repeatability for the quantification of these five components in Cortex Mori with intra‐ and inter‐day standard deviations less than 2.19% and 1.45%, respectively. Conclusion – The validated method was successfully applied to quantify the five investigated components, including a pair of cis‐trans‐isomers 1 and 2 and a pair of isomers 4 and 5 in 34 samples of Cortex Mori from different sources. Copyright © 2010 John Wiley & Sons, Ltd.