Role of the ABC transporter Mdl1 in peptide export from mitochondria

ATP-binding cassette (ABC) adenosine triphosphatases actively transport a wide variety of compounds across biological membranes. Here, the ABC protein Mdl1 was identified as an intracellular peptide transporter localized in the inner membrane of yeast mitochondria. Mdl1 was required for mitochondrial export of peptides with molecular masses of approximately 2100 to 600 daltons generated by proteolysis of inner-membrane proteins by the m-AAA protease in the mitochondrial matrix. Proteolysis by the i-AAA protease in the intermembrane space led to the release of similar-sized peptides independent of Mdl1. Thus, two pathways of peptide efflux from mitochondria exist that may allow communication between mitochondria and their cellular environment.     

An inward-facing conformation of a putative metal-chelate-type ABC transporter

The crystal structure of a putative metal-chelate-type adenosine triphosphate (ATP)-binding cassette (ABC) transporter encoded by genes HI1470 and HI1471 of Haemophilus influenzae has been solved at 2.4 angstrom resolution. The permeation pathway exhibits an inward-facing conformation, in contrast to the outward-facing state previously observed for the homologous vitamin B12 importer BtuCD. Although the structures of both HI1470/1 and BtuCD have been solved in nucleotide-free states, the pairs of ABC subunits in these two structures differ by a translational shift in the plane of the membrane that coincides with a repositioning of the membrane-spanning subunits. The differences observed between these ABC transporters involve relatively modest rearrangements and may serve as structural models for inward- and outward-facing conformations relevant to the alternating access mechanism of substrate translocation.     

ABC转运蛋白介导离子跨膜运输的研究进展

腺苷三磷酸结合盒转运蛋白（ATP-binding cassette transporter,ABC转运蛋白）是一类大量存在于原核生物及真核生物的跨膜转运蛋白,其种类繁多、家族庞大且功能多样,主要功能是利用ATP水解产生的能量将底物进行逆浓度梯度跨膜运输,同时还参与抗原传递、信号传导和细胞解毒等很多重要的生物生理过程。综述了ABC转运蛋白的结构特点、跨膜吸收机制及影响因素,为研究ABC转运蛋白跨膜吸收转运养分离子及其抵抗非生物逆境胁迫提供理论支撑和研究思路。     

Structural basis of trans-inhibition in a molybdate/tungstate ABC transporter

Transport across cellular membranes is an essential process that is catalyzed by diverse membrane transport proteins. The turnover rates of certain transporters are inhibited by their substrates in a process termed trans-inhibition, whose structural basis is poorly understood. We present the crystal structure of a molybdate/tungstate ABC transporter (ModBC) from Methanosarcina acetivorans in a trans-inhibited state. The regulatory domains of the nucleotide-binding subunits are in close contact and provide two oxyanion binding pockets at the shared interface. By specifically binding to these pockets, molybdate or tungstate prevent adenosine triphosphatase activity and lock the transporter in an inward-facing conformation, with the catalytic motifs of the nucleotide-binding domains separated. This allosteric effect prevents the transporter from switching between the inward-facing and the outward-facing states, thus interfering with the alternating access and release mechanism.     

植物ABC转运蛋白功能研究进展

植物ABC转运蛋白家族通过转运各种底物而参与植物一系列生命活动,其拥有众多家族成员,分类众多、结构复杂、功能多样。本文详细梳理了植物ABC转运蛋白的结构、分类及功能后发现,植物类转运蛋白共有8大亚族(ABCA～ABCG和ABCI),其中ABCG属于功能最多的一类亚族,主要参与代谢产物和激素转运、器官形成和物质合成,在重金属/逆境胁迫、以及次级代谢产物分泌等方面发挥着重要作用;ABCB主要参与生长素及重金属转运,刺激细胞生长,加强非生物胁迫的耐受能力;ABCC除参与次生代谢产物的转运外,还具有重金属解毒功能;ABCA类很可能与动植物的脂质代谢关系密切。对于目前功能未知的其他亚族建议开展蛋白互作研究,注重实践应用及多学科联合,更加准确具体解析其功能。全面深入研究植物ABC转运蛋白家族将为其他类转运蛋白的研究提供借鉴方法,同时为植物源/库的高效调控提供基础理论。     

The high-affinity E. coli methionine ABC transporter: structure and allosteric regulation

The crystal structure of the high-affinity Escherichia coli MetNI methionine uptake transporter, a member of the adenosine triphosphate (ATP)-binding cassette (ABC) family, has been solved to 3.7 angstrom resolution. The overall architecture of MetNI reveals two copies of the adenosine triphosphatase (ATPase) MetN in complex with two copies of the transmembrane domain MetI, with the transporter adopting an inward-facing conformation exhibiting widely separated nucleotide binding domains. Each MetI subunit is organized around a core of five transmembrane helices that correspond to a subset of the helices observed in the larger membrane-spanning subunits of the molybdate (ModBC) and maltose (MalFGK) ABC transporters. In addition to the conserved nucleotide binding domain of the ABC family, MetN contains a carboxyl-terminal extension with a ferredoxin-like fold previously assigned to a conserved family of regulatory ligand-binding domains. These domains separate the nucleotide binding domains and would interfere with their association required for ATP binding and hydrolysis. Methionine binds to the dimerized carboxyl-terminal domain and is shown to inhibit ATPase activity. These observations are consistent with an allosteric regulatory mechanism operating at the level of transport activity, where increased intracellular levels of the transported ligand stabilize an inward-facing, ATPase-inactive state of MetNI to inhibit further ligand translocation into the cell.     

谷子ABC转运蛋白基因与抗旱关系的研究

[目的]ABC转运蛋白是一类广泛存在于生物体中最古老的蛋白家族,在植物的生长发育及抗逆胁迫中发挥着重要作用。本文旨在探究ABC转运蛋白基因与谷子抗旱性的关系,挖掘谷子抗旱基因,并为谷子抗旱分子机制的研究提供理论依据。[方法]以谷子抗旱品种勾勾母鸡咀(GG)和干旱敏感品种晋汾16(JF16)为研究材料,在苗期对二者用20%PEG胁迫处理,并取其叶片进行转录组测序,筛选出4个与ABC转运蛋白相关的差异表达基因。用生物信息学方法分析基因的基本信息、启动子顺式元件,并构建ABC抗逆相关基因的系统进化树以及对ABC转运蛋白基因进行表达模式分析。[结果]发现谷子ABC转运蛋白基因等电点范围在6.81~8.97之间,分子量范围在51 195.75~161 579.13Da;启动子中包含有许多响应胁迫的功能元件(ABA、Ethylene、GA、MeJA、Light、MYB、SA、热和低温响应元件等);在进化树分析中发现,Seita.1G039400.1和Seita.7G176000.1亲缘关系最近,其次与AtABCC5亲缘关系较近;经过干旱处理,只有Seita.7G176000.1基因在抗旱品种中表达增加,其余3个基因在抗旱品种中表达均降低。[结论]Seita.7G176000.1基因可能通过调节气孔开闭参与植物抗逆,进而调控谷子响应干旱胁迫,初步推测其为谷子ABC基因家族抗旱候选基因,为进一步研究ABC转运蛋白基因与植物抗逆性关系提供理论依据。     

Structure of the ABC transporter MsbA in complex with ADP.vanadate and lipopolysaccharide

Select members of the adenosine triphosphate (ATP)-binding cassette (ABC) transporter family couple ATP binding and hydrolysis to substrate efflux and confer multidrug resistance. We have determined the x-ray structure of MsbA in complex with magnesium, adenosine diphosphate, and inorganic vanadate (Mg.ADP.Vi) and the rough-chemotype lipopolysaccharide, Ra LPS. The structure supports a model involving a rigid-body torque of the two transmembrane domains during ATP hydrolysis and suggests a mechanism by which the nucleotide-binding domain communicates with the transmembrane domain. We propose a lipid "flip-flop" mechanism in which the sugar groups are sequestered in the chamber while the hydrophobic tails are dragged through the lipid bilayer.     

Localization of iron in Arabidopsis seed requires the vacuolar membrane transporter VIT1

Iron deficiency is a major human nutritional problem wherever plant-based diets are common. Using synchrotron x-ray fluorescence microtomography to directly visualize iron in Arabidopsis seeds, we show that iron is localized primarily to the provascular strands of the embryo. This localization is completely abolished when the vacuolar iron uptake transporter VIT1 is disrupted. Vacuolar iron storage is also critical for seedling development because vit1-1 seedlings grow poorly when iron is limiting. We have uncovered a fundamental aspect of seed biology that will ultimately aid the development of nutrient-rich seed, benefiting both human health and agricultural productivity.     

The E. coli BtuCD structure: a framework for ABC transporter architecture and mechanism

The ABC transporters are ubiquitous membrane proteins that couple adenosine triphosphate (ATP) hydrolysis to the translocation of diverse substrates across cell membranes. Clinically relevant examples are associated with cystic fibrosis and with multidrug resistance of pathogenic bacteria and cancer cells. Here, we report the crystal structure at 3.2 angstrom resolution of the Escherichia coli BtuCD protein, an ABC transporter mediating vitamin B12 uptake. The two ATP-binding cassettes (BtuD) are in close contact with each other, as are the two membrane-spanning subunits (BtuC); this arrangement is distinct from that observed for the E. coli lipid flippase MsbA. The BtuC subunits provide 20 transmembrane helices grouped around a translocation pathway that is closed to the cytoplasm by a gate region whereas the dimer arrangement of the BtuD subunits resembles the ATP-bound form of the Rad50 DNA repair enzyme. A prominent cytoplasmic loop of BtuC forms the contact region with the ATP-binding cassette and appears to represent a conserved motif among the ABC transporters.     

Properties of bursicon: an insect protein hormone that controls cuticular tanning

On gel filtration the retention volume of bursicon indicates a molecular weight of about 40,000. On disc electrophoresis bursicon migrates toward the anode and appears at an R(F) (relative to the marker dye) of 0.3 to 0.4. The properties of fractions with bursicon activity in blood, brain, and ganglion of a fly (Sarcophaga bullata), and in blood, ganglion, and corpora cardiaca of a roach (Periplaneta americana) are similar, but not identical. Bursicon in the blood is more heat labile, and the activity in brain and corpora cardiaca shows two peaks in electrophoresis, instead of one as in the other fractions.     

植物ABC转运蛋白与次生代谢产物的跨膜转运

ABC（ATP-Binding Cassette）转运蛋白是目前已知最大、功能最广泛的蛋白家族，参与生物体内多种物质的转运，因其在生物体内与肿瘤细胞耐药性等一些重要的生理过程密切相关而引起了人们的广泛关注。研究发现，在已完成全基因组测序的生物中，ABC转运蛋白在拟南芥和水稻中数量最多，推测与植物次生代谢产物的跨膜转运相关。植物产生生物碱、萜类化合物、酚类等大量次生代谢产物，保护植物体免受环境中生物和非生物胁迫的损伤。这些化合物的累积和排泌被高度调节，ABC转运蛋白在其中起着重要的作用。本综述介绍了植物ABC转运蛋白及其在植物次生代谢产物累积和跨膜转运中的研究进展。     

Chemical mimicry as an integrating mechanism: cuticular hydrocarbons of a termitophile and its host

The staphylinid beetle Trichopsenius frosti Seevers has the same cuticular hydrocarbons as those of its host termite Reticulitermes flavipes (Kollar) and it biosynthesizes them. These cuticular hydrocarbons probably serve as the primary mechanism by which Trichopsenius frosti integrates itself into the termite colony.     

Plant immunity requires conformational changes [corrected] of NPR1 via S-nitrosylation and thioredoxins

Changes in redox status have been observed during immune responses in different organisms, but the associated signaling mechanisms are poorly understood. In plants, these redox changes regulate the conformation of NPR1, a master regulator of salicylic acid (SA)-mediated defense genes. NPR1 is sequestered in the cytoplasm as an oligomer through intermolecular disulfide bonds. We report that S-nitrosylation of NPR1 by S-nitrosoglutathione (GSNO) at cysteine-156 facilitates its oligomerization, which maintains protein homeostasis upon SA induction. Conversely, the SA-induced NPR1 oligomer-to-monomer reaction is catalyzed by thioredoxins (TRXs). Mutations in both NPR1 cysteine-156 and TRX compromised NPR1-mediated disease resistance. Thus, the regulation of NPR1 is through the opposing action of GSNO and TRX. These findings suggest a link between pathogen-triggered redox changes and gene regulation in plant immunity.     

Uptake of glutamate into synaptic vesicles by an inorganic phosphate transporter

Previous work has identified two families of proteins that transport classical neurotransmitters into synaptic vesicles, but the protein responsible for vesicular transport of the principal excitatory transmitter glutamate has remained unknown. We demonstrate that a protein that is unrelated to any known neurotransmitter transporters and that was previously suggested to mediate the Na(+)-dependent uptake of inorganic phosphate across the plasma membrane transports glutamate into synaptic vesicles. In addition, we show that this vesicular glutamate transporter, VGLUT1, exhibits a conductance for chloride that is blocked by glutamate.     

濒危植物夏蜡梅遗传分化研究

为阐明小尺度范围内濒危物种夏蜡梅种群的遗传分化,保护和恢复夏蜡梅种质资 源,采用 ISSR分子标记技术,对浙江省临安市清凉峰镇的5个夏蜡梅种群的遗传结构进行分析。1 2个引 物对夏蜡梅5个种群100个个体进行扩增,共得到171个位点,其中多态位点98个,总多态 位点百 分率（P）为 57.31%,平均为25.03%。夏蜡梅总Shannon指数 （I）为0.268 9,平均为 0.148 8; 总 Nei指数 （h）为0.174 5,平均为0.102 8。 P、I、h均表明夏蜡梅总体水平的遗传多 样性较高,而种群 水平的遗传多样性较低。AMOVA分子变异分析结果显示,47.01%的变异存在于种群间,5 2.99% 的变异存在于种群内;种群内与种群间的遗传分化均很明显。夏蜡梅种群间基因流较低, 为0.717 3,显示夏蜡梅种群间的基因流动部分受阻。 5个种群的平均遗传距离为0.1051,根据 种群间的遗 传距离进行UPGMA聚类,结果为生境相似的种群聚在一起。夏蜡梅种群间较高水平的遗传 分化 主要是本身的生物学特性以及对微生境适应的结果。     

濒危植物夏蜡梅遗传分化研究

为阐明小尺度范围内濒危物种夏蜡梅种群的遗传分化,保护和恢复夏蜡梅种质资源,采用ISSR分子标记技术,对浙江省临安市清凉峰镇的5个夏蜡梅种群的遗传结构进行分析.12个引物对夏蜡梅5个种群100个个体进行扩增,共得到171个位点,其中多态位点98个,总多态位点百分率(P)为57.31%,平均为25.03%.夏蜡梅总Shannon指数(I)为0.268 9,平均为0.148 8;总Nei指数(h)为0.174 5,平均为0.102 8.P、I、h均表明夏蜡梅总体水平的遗传多样性较高,而种群水平的遗传多样性较低.AMOVA分子变异分析结果显示,47.01%的变异存在于种群间,52.99%的变异存在于种群内;种群内与种群间的遗传分化均很明显.夏蜡梅种群间基因流较低,为0.717 3,显示夏蜡梅种群间的基因流动部分受阻.5个种群的平均遗传距离为0.105 1,根据种群间的遗传距离进行UPGMA聚类,结果为生境相似的种群聚在一起.夏蜡梅种群间较高水平的遗传分化主要是本身的生物学特性以及对微生境适应的结果.