Role of cysteine residues in the NCKX2 Na+/Ca(2+)-K+ Exchanger: generation of a functional cysteine-free exchanger

Cysteine residues play an important role in many proteins, either in enzymatic activity or by mediating inter- or intramolecular interactions. The Na(+)/Ca(2+)-K(+) exchanger plays a critical role in Ca(2+) homeostasis in retinal rod (NCKX1) and cone (NCKX2) photoreceptors by extruding Ca(2+) that enters rod and cone cells via the cGMP-gated channels. NCKX1 and NCKX2 contain five highly conserved cysteine residues. The objectives of this study were threefold: (1) to examine the importance of cysteine residues in NCKX2 protein function; (2) to examine their role in the interaction between NCKX2 and the CNGA subunit of the cGMP-gated channel; and (3) to generate a functional cysteine-free NCKX2 protein. The latter will facilitate structural studies taking advantage of the unique chemistry of the thiol group following insertion of cysteine residues at specific positions in the cysteine-free background. We generated a cysteine-free NCKX2 mutant protein that showed normal protein synthesis and processing and approximately 50% wild-type cation transport function. Cysteine residues were also not critical for the formation of NCKX2 homo-oligmers or NCKX2 hetero-oligomers with the CNGA subunit of the cGMP-gated channel. Our results appear to rule out a critical importance of an intramolecular disulfide linkage in NCKX2 protein synthesis and folding as had been reported before.     

Distribution of Assamese macaques (Macaca assamensis) in the Inner Himalayan region of Bhutan and their mtDNA diversity

The distributions of Assamese macaques (Macaca assamensis) and rhesus macaques (M. mulatta) in Bhutan have been only partially documented. In order to investigate the distribution patterns of these species, we conducted field observation and genetic assessment with mitochondrial DNA (mtDNA) typing of macaques in the Inner Himalayas of Bhutan. There were 24 sightings of macaque groups, and all were visually identified as Assamese macaques. No groups of rhesus macaques were sighted in this survey area, in contrast with the survey results in the Nepalese Himalayas. Molecular phylogenetic analysis revealed that the Bhutan macaques are closer in proximity to their counterparts in the Indo-Chinese region (Thailand and Laos) than to rhesus macaques in China, Laos and India. However, clustering results suggested the marked differentiation of the macaques in Bhutan from the Assamese macaques in Indo-China. We tentatively conclude that the macaques of the Inner Himalayan regions in Bhutan are Assamese macaques and that they appear to be of a lineage distinct from Assamese macaques in the Indo-Chinese region (subspecies M. a. assamensis). The degree of mtDNA diversity suggests that the Assamese macaques in Bhutan are of a more ancient ancestry than M. a. assamensis, thereby supporting the speciation hypothesis of the expansion of a sinica-group of macaques from South Asia to Southeast and then to East Asia (Fooden; Fieldiana Zool 45:1–44, 1988). Assignment of Assamese macaques in Bhutan to M. a. pelops is premature due to the lack of molecular data and recent taxonomic controversy. The mtDNA diversity of Assamese macaques was greater than that of rhesus macaques, suggesting the earlier speciation of Assamese macaques. The significance of the ecogeographic segregation model of macaque distribution is discussed in relation to the evolutionary range expansion into the Himalayan regions in South Asia.     

Population Structure of Wild Musk Shrews (Suncus murinus) in Asia Based on Mitochondrial DNA Variation, with Research in Cambodia and Bhutan

The musk shrew (Suncus murinus) is a small mammalian species belonging to Insectivora. It is widely distributed in Asia. To identify the genetic relationship among wild musk shrew populations and examine its migration route, we investigated the populations of Cambodia and Bhutan by using mitochondrial DNA restriction fragment length polymorphism analysis and compared them with other Asian populations previously described. Four haplotypes were detected in Cambodia and eight in Bhutan. A total of 53 haplotypes were detected in Asia and were classified largely into two groups, the Continental and Island types, based on a minimum spanning network. From the distribution of mtDNA types in wild musk shrews, three major population groups are identified in Asia: South Asia, Southeast Asia, and Malay. It is suggested that the Malay population group was a mix of South and Southeast Asian population groups and that this was a contact area of the two groups. In addition, other contact areas between the South and Southeast Asian groups exist in Myanmar, but unlike the Malay, the Myanmar area was the border of these groups.     

Chemical composition of the essential oils of two Rhodiola species from Tibet

The essential oils from rhizomes of Rhodiola crenulata and R. fastigiata in eastern Tibet were analyzed by using GC-MS. The major constituents were geraniol (53.3%), n-octanol (13.4%), 2-methyl-3-buten-2-ol (10.8%), citronellol (5.3%), 3-methyl-2-buten-1-ol (4.0%), myteol (3.0%), and linalool (2.4%) for R. crenulata and geraniol (45.3%), n-octanol (12.3%), 2-methyl-3-buten-2-ol (8.0%), linalool (5.1%), isogeraniol (4.5%), citronellol (4.4%), and cis-sabinenehydrate (3.6%) for R. fastigiata.     

Phylogeography of Wild Musk Shrew (Suncus Murinus) Populations in Asia Based on Blood Protein/Enzyme Variation

The musk shrew (Suncus murinus) is an insectivore species that inhabits tropical and subtropical Asia widely. To clarify the genetic relationship among wild musk shrew populations, we examined the electrophoretic variants of biparentally inherited genetic markers at 10 loci coding for eight blood proteins/enzymes in a total of 639 animals and compared the results obtained from the mitochondrial DNA data. The principal-component analysis performed using the allele frequency data revealed that the 17 populations could be divided into two major groups, a South Asian group and a Southeast Asian group that includes several island populations bound by Myanmar. The degrees of genetic divergence among populations were higher within the Southeast Asian group than within the South Asian group. This finding was incongruent with the mtDNA diversity. Analysis conducted at the individual level showed that a shrew from the central region in Myanmar that carries a South Asian type of mtDNA showed the electrophoretic variants specific to the Southeast Asian group, suggesting that this region is a contact zone between the two major groups.     

72份青稞氨基酸组成与营养价值评价

为了解青稞氨基酸的组成及营养品质,本研究测定了72份青稞材料籽粒的17种氨基酸(色氨酸除外)含量,通过对供试青稞材料氨基酸含量进行聚类分析,并比较育成品种与地方品种的氨基酸组成差异,对青稞的氨基酸进行了营养价值评价。结果表明,青稞氨基酸总含量平均为87.454 mg/g DW,变幅为47.8~178.7 mg/g DW,其中必需氨基酸含量占37.15%,谷氨酸的含量最高且变异大,蛋氨酸含量最低,赖氨酸含量变异小,91.67%的青稞材料的第一限制性氨基酸为赖氨酸。青稞氨基酸的贴近度为0.903,与世界粮农组织(FAO)、世界卫生组织(WHO)、联合国大学(UNU)提出的模式蛋白质的必需氨基酸组成较接近,氨基酸比值系数分SRC(73.14)较高。非必需氨基酸占青稞总氨基酸含量的62.85%,其中鲜味和甜味氨基酸含量分别为26.58 mg/g DW和21.85 mg/g DW,分别占总氨基酸含量的30.04%和24.43%。不同青稞材料的氨基酸含量和营养价值有很大的差异,地方品种各氨基酸含量均高于育成品种。供试材料中有4份青稞的氨基酸营养价值及风味氨基酸含量均较高。研究结果可为优质氨基酸组成的青稞选育及青稞加工提供指导。     

Understanding Land Use, Livelihoods, and Health Transitions among Tibetan Nomads: A Case from Gangga Township, Dingri County, Tibetan Autonomous Region of China

Tibetan nomads in the Tibetan Autonomous Region of China have experienced profound transitions in recent decades with important implications for land use, livelihoods, and health development. The change from being traditional nomads to agropastoralists engaged in permanent agriculture, a sedentary village life (known as “sedentarization”), has been associated with a remarkable change in diet and lifestyle, decline in spatial mobility, increase in food production, and emerging infectious and noncommunicable diseases. The overarching response of the government has been to emphasize infrastructure and technological solutions. The local adaptation strategies of Tibetan nomads through maintaining balanced mobile herding, reindeer husbandry, as well as off-farm labor and trade could address both the cause of environmental degradation and improve the well-being of local people. Drawing on transdisciplinary, preliminary field work in Gangga Township of Dingri County in the foothills of Mt. Everest, we identify pertinent linkages between land use and health, and spatial and temporal mismatch of livelihoods and health care services, in the transition to sedentary village life. We suggest emerging imperatives in Ecohealth to help restore Tibetan livelihoods in transition to a sedentary lifestyle.     

Topology of the retinal cone NCKX2 Na/Ca-K exchanger

The Na/Ca-K exchanger (NCKX) is a polytopic membrane protein that plays a critical role in Ca(2+) homeostasis in retinal rod and cone photoreceptors. The NCKX1 isoform is found in rods, while the NCKX2 isoform is found in cones, in retinal ganglion cells, and in various parts of the brain. The topology of the Na/Ca-K exchanger is thought to consist of two large hydrophilic loops and two sets of transmembrane spanning segments (TMs). The first large hydrophilic loop is located extracellularly at the N-terminus; the other is cytoplasmic and separates the two sets of TMs. The TMs consist of either five and five membrane spanning helices or five and six membrane spanning helices, depending upon the predictive algorithm used. Little specific information is yet available on the orientation of the various membrane spanning helices and the localization of the short loops connecting these helices. In this study, we have determined which of the connecting loops are exposed to the extracellular milieu using two different methods: accessibility of substituted cysteine residues and insertion of N-glycosylation sites. The two methods resulted in a consistent NCKX topology in which the two sets of TMs each contain five membrane spanning helices. Our new model places what was previously membrane spanning helix six in the cytoplasm, which places the C-terminus on the extracellular surface. Surprisingly, this NCKX topology model is different from the current NCX topology model with respect to the C-terminal three membrane helices.