The CC1-FHA Tandem as a Central Hub for Controlling the Dimerization and Activation of Kinesin-3 KIF1A

Kinesin-3 KIF1A plays prominent roles in axonal transport and synaptogenesis. KIF1A adopts?a monomeric form in?vitro but acts as a processive dimer in?vivo. The mechanism underlying the motor dimerization is poorly understood. Here, we find that the CC1-FHA tandem of KIF1A exists as a stable dimer. The structure of CC1-FHA reveals that the linker between CC1 and FHA unexpectedly forms a β-finger hairpin, which integrates CC1 with FHA assembling a CC1-FHA homodimer. More importantly, dissociation of the CC1-FHA dimer unleashes CC1 and the β-finger, which are both essential for the motor inhibition. Thus, dimerization of the CC1-FHA tandem not only promotes the KIF1A dimer formation but also may trigger the motor activity via sequestering the CC1/β-finger region. The CC1-FHA tandem likely functions as a hub for controlling the dimerization and activation of KIF1A, which may represent?a new paradigm for the kinesin regulation shared by other kinesin-3 motors.     

Derivation of human embryonic stem cells with NEMO deficiency

Deficiency of the nuclear factor-kappa-B essential modulator (NEMO) is a rare X-linked disorder that presents in boys as hypohydrotic ectodermal dysplasia with immunodeficiency due to defective nuclear factor-κB activation. Here we report on the generation of 2 human embryonic stem cell lines from discarded in vitro fertilization (IVF) embryos ascertained via preimplantation genetic diagnosis. We have derived two human embryonic stem cell lines that carry a T458G hypomorphic mutation in exon 4 of the NEMO (or IKBKG) gene. One of the lines is diploid male; the other is diploid female but has clonally inactivated the X-chromosome that harbors the wild-type IKBKG gene. We show that both lines are pluripotent, have the capacity to differentiate into hematopoietic progenitors, and have defective inhibitor of nuclear factor kappa-B kinase activity. These NEMO deficiency hES cell lines provide an unlimited source for differentiated cell types and may serve as a unique tool to study NEMO deficiency and potentially lead to the development of new therapies for this disease.     

Genome Sequence of Borrelia afzelii Strain HLJ01, Isolated from a Patient in China

We report here the genome sequence of Borrelia afzelii strain HLJ01, isolated from a patient with Lyme disease in China. It is the first report of the whole genome of a B. burgdorferi sensu lato isolate from a human in China.     

Human protein-disulfide isomerase is a redox-regulated chaperone activated by oxidation of domain a'

Protein-disulfide isomerase (PDI), with domains arranged as abb'xa'c, is a key enzyme and chaperone localized in the endoplasmic reticulum (ER) catalyzing oxidative folding and preventing misfolding/aggregation of proteins. It has been controversial whether the chaperone activity of PDI is redox-regulated, and the molecular basis is unclear. Here, we show that both the chaperone activity and the overall conformation of human PDI are redox-regulated. We further demonstrate that the conformational changes are triggered by the active site of domain a', and the minimum redox-regulated cassette is located in b'xa'. The structure of the reduced bb'xa' reveals for the first time that domain a' packs tightly with both domain b' and linker x to form one compact structural module. Oxidation of domain a' releases the compact conformation and exposes the shielded hydrophobic areas to facilitate its high chaperone activity. Thus, the study unequivocally provides mechanistic insights into the redox-regulated chaperone activity of human PDI.     

Maternal Mortality in Henan Province,China: Changes between 1996 and 2009

Background

Maternal deaths occur mostly in developing countries and the majority of them are preventable. This study analyzes changes in maternal mortality and related causes in Henan Province, China, between 1996 and 2009, in an attempt to provide a reliable basis for introducing effective interventions to reduce the maternal mortality ratio (MMR), part of the fifth Millennium Development Goal.

Methods and Findings

This population-based maternal mortality survey in Henan Province was carried out from 1996 to 2009. Basic information was obtained from the health care network for women and children and the vital statistics system, from specially trained monitoring personnel in 25 selected monitoring sites and by household survey in each case of maternal death. This data was subsequently reported to the Henan Provincial Maternal and Child Healthcare Hospital. The total MMR in Henan Province declined by 78.4%, from 80.1 per 100 000 live births in 1996 to 17.3 per 100 000 live births in 2009. The decline was more pronounced in rural than in urban areas. The most common causes of maternal death during this period were obstetric hemorrhage (43.8%), pregnancy-induced hypertension (15.8%), amniotic fluid embolism (13.9%) and heart disease (8.0%). The MMR was higher in rural areas with lower income, less education and poorer health care.

Conclusion

There was a remarkable decrease in the MMR in Henan Province between 1996 and 2009 mainly in the rural areas and MMR due to direct obstetric causes such as obstetric hemorrhage. This study indicates that improving the health care network for women, training of obstetric staff at basic-level units, promoting maternal education, and increasing household income are important interventional strategies to reduce the MMR further.     

Ultrasensitive and selective non-enzymatic glucose detection using copper nanowires

In the pursuit of more economical electrocatalysts for non-enzymatic glucose sensors, one-dimensional Cu nanowires (Cu NWs) with uniform size distribution and a large aspect ratio (>200) were synthesized by a facile, scalable, wet-chemistry approach. The morphology, crystallinity, and surface property of the as-prepared Cu NWs were examined by SEM, XRD, and XPS, respectively. The electrochemical property of Cu NWs for glucose electrooxidation was thoroughly investigated by cyclic voltammetry. In the amperometric detection of glucose, the Cu NWs modified glassy carbon electrode exhibited an extraordinary limit of detection as low as 35 nM and a wide dynamic range with excellent sensitivity of 420.3 μA cm(-2) mM(-1), which was more than 10,000 times higher than that of the control electrode without Cu NWs. The performance of the developed glucose sensor was also independent to oxygen concentration and free from chloride poisoning. Furthermore, the interference from uric acid, ascorbic acid, acetaminophen, fructose, and sucrose at the level of their physiological concentration were insignificant, indicating excellent selectivity. Finally, good accuracy and high precision for the quantification of glucose concentration in human serum samples implicate the applicability of Cu NWs in sensitive and selective non-enzymatic glucose detection.     

Toward nitrogen neutral biofuel production

Environmental concerns and an increasing global energy demand have spurred scientific research and political action to deliver large-scale production of liquid biofuels. Current biofuel processes and developing approaches have focused on closing the carbon cycle by biological fixation of atmospheric carbon dioxide and conversion of biomass to fuels. To date, these processes have relied on fertilizer produced by the energy-intensive Haber-Bosch process, and have not addressed the global nitrogen cycle and its environmental implications. Recent developments to convert protein to fuel and ammonia may begin to address these problems. In this scheme, recycling ammonia to either plant or algal feedstocks reduces the demand for synthetic fertilizer supplementation. Further development of this technology will realize its advantages of high carbon fixation rates, inexpensive and simple feedstock processing, in addition to reduced fertilizer requirements.     

A novel sucrose phosphorylase from the metagenomes of sucrose-rich environment: isolation and characterization

Sucrose phosphorylase, an important enzyme mainly involved in the generic starch and sucrose pathways, has now caught the attention of researchers due to its transglycosylation activity. A novel sucrose phosphorylase, unspase, has been isolated, and its transglycosylation properties were characterized. Compared with Bisp, the sucrose phosphorylase from Bifidobacterium adolescentis, unspase had two deleted regions in its C: -terminal. These deleted regions were probably equivalent to the important five-stranded anti-parallel β-sheet domain in sucrose phosphorylase. Unspase has a k(m) of 21.12?mM, a V(max) of 69.24?μmol?min(-1)?mg(-1) and a k(cat) of 31.19?s(-1) with sucrose as substrate. In 3-(N-morpholino) propanesulfonic acid (MOPS) buffer, unspase transferred the glycosyl moiety to L: -arabinose, D: -fructose and L: -sorbose. Much to our surprise, unspase can catalyze the transglycosylation in which a glycosyl moiety was transferred to L: -arabinose in the presence of phosphate, which is an interesting exception to the generally accepted fact that transglycosylation can only occur under the condition of phosphate absence. The final yield of the transglycosylation product (37.9?%) in phosphate buffer was even higher than that (5.8?%) in MOPS buffer. This is a novel phenomenon that a sucrose phosphorylase can catalyze a transglycosylation reaction in the presence of phosphate.     

Stable isotope-labelling analysis of the impact of inhibition of the mammalian target of rapamycin on protein synthesis

mTORC1 [mTOR (mammalian target of rapamycin) complex 1] regulates diverse cell functions. mTORC1 controls the phosphorylation of several proteins involved in mRNA translation and the translation of specific mRNAs, including those containing a 5'-TOP (5'-terminal oligopyrimidine). To date, most of the proteins encoded by known 5'-TOP mRNAs are proteins involved in mRNA translation, such as ribosomal proteins and elongation factors. Rapamycin inhibits some mTORC1 functions, whereas mTOR-KIs (mTOR kinase inhibitors) interfere with all of them. mTOR-KIs inhibit overall protein synthesis more strongly than rapamycin. To study the effects of rapamycin or mTOR-KIs on synthesis of specific proteins, we applied pSILAC [pulsed SILAC (stable isotope-labelling with amino acids in cell culture)]. Our results reveal, first, that mTOR-KIs and rapamycin differentially affect the synthesis of many proteins. Secondly, mTOR-KIs inhibit the synthesis of proteins encoded by 5'-TOP mRNAs much more strongly than rapamycin does, revealing that these mRNAs are controlled by rapamycin-insensitive outputs from mTOR. Thirdly, the synthesis of certain other proteins shows a similar pattern of inhibition. Some of them appear to be encoded by 'novel' 5'-TOP mRNAs; they include proteins which, like known 5'-TOP mRNA-encoded proteins, are involved in protein synthesis, whereas others are enzymes involved in intermediary or anabolic metabolism. These results indicate that mTOR signalling may promote diverse biosynthetic processes through the translational up-regulation of specific mRNAs. Lastly, a SILAC-based approach revealed that, although rapamycin and mTOR-KIs have little effect on general protein stability, they stabilize proteins encoded by 5'-TOP mRNAs.