A Mn(II)–Mn(II) center in human prolidase

Human prolidase, the enzyme responsible for the hydrolysis of the Xaa-Pro/Hyp peptide bonds, is a key player in the recycling of imino acids during the final stage of protein catabolism and extracellular matrix remodeling. Its metal active site composition corresponding to the maximal catalytic activity is still unknown, although prolidase function is of increasing interest due to the link with carcinogenesis and mutations in prolidase gene cause a severe connective tissue disorder. Here, using EPR and ICP-MS on human recombinant prolidase produced in Escherichia coli (hRecProl), the Mn(II) ion organized in a dinuclear Mn(II)–Mn(II) center was identified as the protein cofactor. Furthermore, thermal denaturation, CD/fluorescence spectroscopy and limited proteolysis revealed that the Mn(II) is required for the proper protein folding and that a protein conformational modification is needed in the transition from apo- to Mn(II)loaded-enzyme. The collected data provided a better knowledge of the human holo-prolidase and, although limited to the recombinant enzyme, the exact identity and organization of the metal cofactor as well as the conformational change required for activity were proven.     

Foliar Mn accumulation in eastern Australian herbarium specimens: prospecting for ��new�� Mn hyperaccumulators and potential applications in taxonomy

Background and Aims

The analysis of herbarium specimens has previously been used to prospect for ‘new’ hyperaccumulators, while the use of foliar manganese (Mn) concentrations as a taxonomic tool has been suggested. On the basis of their geographic and taxonomic affiliations to known Mn hyperaccumulators, six eastern Australian genera from the Queensland Herbarium collection were sampled for leaf tissue analyses.

Methods

ICP-OES was used to measure Mn and other elemental concentrations in 47 species within the genera Austromyrtus, Lenwebbia, Gossia (Myrtaceae), Macadamia (Proteaceae), Maytenus and Denhamia (Celastraceae).

Key Results

The resulting data demonstrated (a) up to seven ‘new’ Mn hyperaccumulators, mostly tropical rainforest species; (b) that one of these ‘new’ Mn hyperaccumulators also had notably elevated foliar Ni concentrations; (c) evidence of an interrelationship between foliar Mn and Al uptake among the Macadamias; (d) considerable variability of Mn hyperaccumulation within Gossia; and (e) the possibility that Maytenus cunninghamii may include subspecies.

Conclusions

Gossia bamagensis, G. fragrantissima, G. sankowsiorum, G. gonoclada and Maytenus cunninghamii were identified as ‘new’ Mn hyperaccumulators, while Gossia lucida and G. shepherdii are possible ‘new’ Mn hyperaccumulators. Of the three Myrtaceae genera examined, Mn hyperaccumulation appears restricted to Gossia, supporting its recent taxonomic revision. In the context of this present investigation and existing information, a reassesment of the general definition of Mn hyperaccumulation may be warranted. Morphological variation of Maytenus cunninghamii at two extremities was consistent with variation in Mn accumulation, indicating two possible ‘new’ subspecies. Although caution should be exercised in interpreting the data, surveying herbarium specimens by chemical analysis has provided an effective means of assessing foliar Mn accumulation. These findings should be followed up by field studies.Key words: Gossia bamagensis, G. fragrantissima, G. sankowskiorum, G. gonoclada, G. lucida, G. shepherdii, Maytenus cunninghamii, Mn hyperaccumulator     

Model Compounds of the Mn Cluster in Oxygen-evolving Complex of PS￠ò

Six model compounds have been synthesized and used for probing the structural features of the Mn cluster in oxygen-evolving complex (OEC) of photosystem Ⅱ (PSⅡ). The model compounds contain Mn2(μ-O) 2 and μ-O-μ-carboxylato di-manganese structural units, which offer Mn—Mn, Mn……Mn, and Mn—O(N) structural parameters consistent with the corresponding data of the OEC in PSⅡ, implying that the Mn cluster in OEC may possess similar structural features. Two model compounds containing halide anion have been used for discussing the binding of Cl- to Mn in PSⅡ. It is suggested that in the five S states, ligand exchange would lead to the ligation of chloride to Mn in the S states with Mn of higher valence.     

Review of NMR and μSR studies in the molecular nanomagnet Mn12-ac

We present a comprehensive review of the NMR and μSR studies performed in the molecular nanomagnet Mn12 a system characterized and widely studied by Prof. Gatteschi’s group in Florence. The proton (¹H, ²D) NMR, the ⁵⁵Mn NMR and the μSR investigations have yielded important information regarding both static and dynamic magnetic properties of the molecule. The magnetic and quadrupole hyperfine interactions have been extracted from NMR data. The spin dynamics at high and intermediate temperature associated with the zero dimensionality and with the spin–phonon coupling has been studied together with the spin dynamics in the quantum tunneling low temperature regime. The local spin configuration in the giant S = 10 total spin ground state has been determined via ⁵⁵Mn NMR in zero magnetic field and with fields parallel and perpendicular to the anisotropy axis. Finally a novel method is described to monitor the relaxation of the magnetization from the time evolution of the NMR spectrum.     

北方土壤中Mn的形态及其与活性Mn的关系

用逐步连续分级浸提法研究了我国北方主要土壤中Mn的存在形态及其与活性Mn的关系.碱性土壤中Mn的形态分布特征为氧化锰态Mn>残留态Mn>有机质结合态Mn>无定形铁结合态Mn>晶形铁结合态Mn>代换态Mn,与酸性土壤的排列顺序明显不同.碱性上壤条件导致土壤中的Mn更多地向生物无效态转化,使得土壤的活性Mn主要以氧化锰态和代换态存在.     

Degradation of DNA into 5′-Monodeoxyribonucleotides in the Presence of Mn2+ Ions

DNA is known to be aggregated by metal ions including Mn²⁺ ions, but analysis of the aggregation process from a chemical viewpoint, which means identification of the product yielded during the process, has not been performed yet. On examination of the kinds of degraded materials that were in the supernatant obtained on centrifugation of a DNA mixture aggregated under conditions of 10 mM Mn²⁺ ions ([Mn]/[P] = 46.3) at 70 °C for 1 h, the degradation products were found to be dAMP, dCMP, dGMP, and TMP. These dNMPs were purified by HPLC on TSKgel ODS-80Ts and identified by LC-TOF/MS. The degradation activity was lost on pretreatment of the DNA with a phenol–chloroform mixture, and the activity was recovered by pretreatment with a mixture of DMSO and a buffer containing surfactants. Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺, as transition element metal ions, were effective as to the degradation into dNMP. Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, as alkali earth element metal ions, were not effective as to the degradation. Monovalent anions such as Cl^?, CH₃OO^?, and NO₃ ^? were found to increase the degradation rate. Sixty μg of the 120 μg of the starting DNA in 450 μl was degraded into dNMP on reaction for 1 h in the presence of 100 mM NaCl and 10 mM Mn²⁺ ions. In this process, aggregation did not occur, and thus was not considered to be necessary for degradation. The degradation was found not to occur at pH 7.0, and to be very sensitive to pH. The OH^? ion should have a critical role in cleavage of the phosphodiester linkages in this case. The dNMP obtained in the degradation process was found to be only 5′-NMP, based on the H¹NMR spectra. This prosess should prove to be a new process for the production of 5′-dNMP in addtion to the exonuclease.     

土壤施Mn深度对不同基因型小麦缺Mn的影响

以缺Mn土壤为基质进行的小麦模拟土柱试验结果表明,不同施Mn深度条件下3317和川麦222个小麦基因型的缺Mn症、产量、根系分布和体内Mn含量均存在着显着差异。随着施Mn深度的增加,Mn肥的增产效果更为明显,川麦22施Mn的增产幅度高于3317.初步认为,3317耐缺Mn能力高于川麦22,与其根系在中下部土层分布比例高,吸Mn能力强有关。土柱试验发现小麦苗期的缺Mn症在中下部土层供Mn时明显恢复,表明中后期供Mn对小麦产量的形成有至关重要的作用.     

人Mn—SOD基因结构

人Ｍｎ┐ＳＯＤ基因结构吕星孙志贤裴雪涛吴祖泽（北京放射医学研究所,北京１００８５０）关键词锰超氧化物歧化酶基因结构超氧化物歧化酶（ｓｕｐｅｒｏｘｉｄｅｄｉｓｍｕ－ｔａｓｅ,ＳＯＤ）催化超氧阴离子自由基（Ｏ－·２）转变为Ｈ２Ｏ２和Ｏ２的歧化反应（２Ｏ－...     

Carbon quantity and quality drives variation in cave microbial communities and regulates Mn(II) oxidation

Cave ecosystems are carbon limited and thus are particularly susceptible to anthropogenic pollution. Yet, how carbon quality and quantity that can modulate the pathways and amount of Mn cycling in caves remains largely unknown. To explore Mn cycling, baseline bacterial, archaeal, and fungal communities associated with Mn(III/IV) oxide deposits were assessed in both relatively ‘pristine’ and anthropogenically impacted caves in the Appalachian Mountains (USA). Cave sites were then amended with various carbon sources that are commonly associated with anthropogenic input to determine whether they stimulate biotic Mn(II) oxidation in situ. Results revealed patterns between sites that had long-term exogenous carbon loading compared to sites that were relatively ‘pristine,’ particularly among Bacteria and Archaea. Carbon treatments that stimulated Mn(II) oxidation at several sites resulted in significant changes to the microbial communities, indicating that anthropogenic input can not only enhance biotic Mn(II) oxidation, but also shape community structure and diversity. Additional carbon sources amended with copper were incubated at various cave sites to test the role that Cu(II) plays in in situ biotic Mn(II) oxidation. Media supplemented with 100 µM Cu(II) inhibited bacterial Mn(II) oxidation but stimulated fungal Mn(II) oxidation, implicating fungal use of multicopper oxidase (MCO) enzymes but bacterial use of superoxide to oxidize Mn(II). In sites with low C:N ratios, the activity of the Mn(II) oxidizing enzyme manganese peroxidase (MnP) appears to be limited (particularly by MnP-utilizing Basidiomycetes and/or Zygomycetes).     

Reductive Dechlorination of Trichloroethylene (TCE) in Competition with Fe and Mn Oxides—Observed Dynamics in H2-dependent Terminal Electron Accepting Processes

The determination of hydrogen (H₂) concentration together with the products of microbial reduction reactions in a trichloroethylene dechlorinating system is conducted to delineate the ongoing predominant terminal electron accepting processes (TEAP). Formate was used as electron donor and synthetic Fe minerals or environmental samples were used as the substrate. Iron(III) and Mn(IV) reduction limited microbial dechlorination by the mixed anaerobic culture by decreasing the level of H₂ in the system. The H₂ measurements indicated that the H₂ concentration at which different TEAPs occur can overlap and thus these TEAPs can therefore occur concurrently rather than exclusively. Difference in Fe(III) bioavailability and hence, Fe(III) reduction partially explain this wide range. The distinction between dechlorination and other microbial reduction processes based on H₂ threshold values is not feasible under such conditions, though there appears to be a relation between the rates of H₂ consuming process and the observed H₂ level.     

Evidence for σ → η3 rearrangement reaction in gaseous ions from Fe,Mn and Re allylic derivatives

The fragmentation pathways of (η³-C₃H₄X)FeCO)₂NO, (σ-C₃H₄X)Fe(CO)₂(NO)L, (η³-C₃H₄X)Fe(CO)(NO)L, (σ-C₃H₄X)Fe(CO)₂(NO)L′, (η³- C₃H₄X)Fe(CO)(NO)L′, (σ-C₃H₅)M(CO)₅, (η³-C₃H₅)M(CO)₄, (σ-CH₂CHC(Me)₂)Mn(CO)₅, (η³-CH₂ CHC(Me)₂)Mn(CO)₄, (X=2-Cl; L=PPh₃; L′= P(OMe)₃; M=Mn, Re) have been investigated by mass spectrometry. In the σ derivatives the molecular ion loses CO or the allylic ligand, while in the η³ derivative loss of a CO group is the only fragmentation mode of the molecular ion. Electron impact as well as methane chemical ionization mass spectra have been reported. Kinetic energy release of selected metastable ions indicates that a σ → η³ rearrangement reaction occurs.     

九州虫草菌丝体对Mn的耐性及富集

重金属耐性真菌的研究是生物修复的重要研究内容。本文研究了九州虫草（Cordyceps kyusyuensis）对于Mn的耐性及富集。在液体培养基中添加不同浓度（0—60 g/L）的Mn离子,测定其菌丝生物量、菌丝Mn含量、菌丝抗氧化酶活性和过氧化水平以及菌体细胞离子交换量、Mn在细胞中的分布的变化情况。实验结果表明九州虫草菌丝生物量与Mn浓度呈显著负相关,Mn浓度60 g/L为九州虫草菌丝生长极限浓度。菌丝中Mn含量随培养基中Mn浓度的增大而显著升高,10 g/L Mn时,菌丝细胞中Mn积累量达到细胞干重的1.0013%。九州虫草菌丝中过氧化产物丙二醛（MDA）、可溶性蛋白（SP）含量、可溶性糖浓度与培养基中Mn浓度呈负相关,实验组与对照组差异显著。抗氧化酶（过氧化氢酶（CAT）、过氧化物酶（POD）、超氧化物歧化酶（SOD））活性随着培养基中Mn浓度增大而显著升高,但变化趋势不同。九州虫草菌丝细胞不可溶性组分中Mn的量（91.51%—98.6%）显著高于可溶部分（1.40%—8.49%）。九州虫草菌丝细胞壁离子交换量（CEC）随着培养基中Mn浓度的升高变化不明显。说明在九州虫草菌丝对Mn的富集过程中,其细胞壁、细胞膜和细胞器对于Mn结合发挥了主要作用,细胞质中可溶性成分对Mn的结合发挥次要作用。在Mn的胁迫下,增强抗氧化酶系统的协同作用以清除大量自由基是细胞对锰耐性的重要机制。     

EPR and magnetic properties of [Mn(μ-Cl)2(bpy)]n: An unusual ferromagnetic interaction in a Mn(II) chloro-bridged polymer

The study of the magnetic properties and EPR spectra of the one-dimensional bis(μ-chloro) Mn(II) polymer [Mn(μ-Cl)₂(bpy)]_n (1) (bpy = 2,2′-bipyridine) is reported. Magnetic susceptibility measurements reveal a weak ferromagnetic interaction between the Mn(II) ions (J = +0.19 cm⁻¹). This is the first polymer of six-coordinated Mn(II) ions with a [Mn₂(μ-Cl)₂]²⁺ magnetic repeating unit, showing a ferromagnetic interaction. The coordination octahedra are elongated in the Cl?Cl direction and the elongation axes are parallel along the chain. Extended Hückel calculations show that the octahedra share an equatorial-apical edge, with the equatorial plane being parallel, and perpendicular to the Mn₂(μ-Cl)₂. Due to this disposition, the overlap through the chloride bridges is small, so the antiferromagnetic contribution must also be small and, therefore, a ferromagnetic behaviour is observed. The EPR spectra of a polycrystalline sample of 1 at different temperatures are also reported. A variation of the bandwidth with temperature is observed, which could be because this ferromagnetic interaction is weak: above 150 K the dipolar interaction is the predominant effect, while below 150 K the magnetic exchange interaction dominates.     

Molecular and expression analysis of manganese superoxide dismutase (Mn–SOD) gene under temperature and starvation stress in rotifer Brachionus calyciflorus

Superoxide dismutase (SOD) is an important antioxidant enzyme that protects organs from damage by reactive oxygen species. We cloned cDNA encoding SOD activated with manganese (Mn–SOD) from the rotifer Brachionus calyciflorus Pallas. The full-length cDNA of Mn–SOD was 1,016 bp and had a 669 bp open reading frame encoding 222 amino acids. The deduced amino acid sequence of B. calyciflorus Mn–SOD showed 89.1, 71.3, and 62.1 % similarity with the Mn–SOD of the marine rotifer Brachionus plicatilis, the nematode Caenorhabditis elegans, and the fruit fly Drosophila melanogaster, respectively. The phylogenetic tree constructed based on the amino acid sequences of Mn–SODs from B. calyciflorus and other organisms revealed that this rotifer is closely related to nematodes. Analysis of the mRNA expression of Mn–SOD under different conditions revealed that expression was enhanced 5.6-fold (p < 0.001) at 30 °C after 2 h, however, low temperature (15 °C) promoted Mn SOD temporarily (2.5-fold, p < 0.001) and then decreased to normal level (p > 0.05). Moderate starvation promoted Mn–SOD mRNA expression (p ₁₂ < 0.01, p ₃₆ < 0.05), which reached a maximum value (15.3 times higher than control, p ₂₄ < 0.01) at 24 h. SOD and CAT activities also elevated at the 12 h–starved group. These results indicate that induction of Mn–SOD expression by stressors likely plays an important role in aging of B. calyciflorus.     

Thermodynamics of Mn2+-binding to goat α-lactalbumin

By means of reaction calorimetry we measured the apparent enthalpy change, H^app, of the binding of Mn²⁺-ions to goat -lactalbumin as a function of temperature. The observed H^app can be written as the sum of contributions resulting from a conformational and a binding process. In combination with the thermal unfolding curve of goat -lactalbumin, we succeeded in separating the complete set of thermodynamic parameters (H, G, S, C_p) into the binding and conformational contributions. By circular dichroism we showed that NH ₄ ⁺ -ions, upon binding to bovine a-lactalbumin, induce the same conformational change as do Na⁺ and K⁺: the binding constant equals 98 ± 9 M^–1.Abbreviations BLA bovine -lactalbumin - GLA goat -lactalbumin - HLA human -lactalbumin - CD circular dichroism Offprint requests to: H. Van DaelDeceased     

Calorimetric experiments of Mn2+-binding to α-lactalbumin

We measured by batch microcalorimetry the standard enthalpy change ΔH° of the binding of Mn²⁺ to apo-bovine α-lactalbumin; ΔH° = −90 ± 4kJ·mol⁻¹. The binding constants, K_Mn²⁺, calculated from the calorimetric and circular dichroism titration curves, are (4.6±1) · 10⁵M⁻¹, respectively. Batch calorimetry confirms the competitive binding of Ca²⁺, Mn²⁺ and Na⁺ to the same site. The relatively small enthalpy change for Mn²⁺ binding compared to Ca²⁺ binding favours a model of a rigid and almost ideal Ca²⁺-complexating site, different from the well-known EF-hand structures. Cation binding to the high-affinity site most probably triggers the movement of an α-helix which is directly connected to the complexating loop.     

人Mn—SOD cDNA的克隆及高效表达

用逆转录－聚合酶链反应（ＲＴ－ＰＣＲ）,以人肝细胞株（Ｌ０２）总ＲＮＡ为模板,扩增了人锰超氧化物歧化酶（ｈＭｎ－ＳＯＤ）的ｃＤＮＡ。重组到Ｔ７启动子控制下的表达载体ｐＥＴ－２４ａ（＋）中,构建表爱质粒ｐＥＴ－ＭｎＳＯＤ,并转化大肠杆菌ＢＬ２１（ＤＥ３）。ＳＤＳ－ＰＡＧＥ及蛋白质印迹分析表明,经１ｍｍｏｌ／Ｌ异丙基硫代－β－Ｄ－半乳糖苷（ＩＰＴＧ）诱导后,可高效表达一分子量为２２ｋＤ的蛋白质,与抗人     

环境条件对不同品种小麦缺Mn的影响

在温室和网室中进行盆栽试验 ,研究不同环境条件和杂草对冬小麦缺Mn的影响 ,同时探讨不同小麦品种对缺Mn的耐性 ,发现生长在温室中的小麦其缺Mn症尤为严重 ,而从网室转移到温室的小麦因苗期在网室中受降雨渍水影响吸收了较多Mn2 ,缺Mn症就较轻 ,表明环境因子中降雨是影响小麦Mn营养的一个重要因素 ;供试的 3个品种中 331 7较耐缺Mn ,其Mn的吸收量明显高于敏感品种 .此外 ,试验还发现与小麦伴生的杂草麦麦草对Mn吸收能力强 ,是小麦根际Mn营养的有力争夺者 .