Large-scale purification and characterization of calmodulin from ram testis its metal-ion-dependent conformers

Calmodulin was isolated in large quantities from ram testis by a simple procedure involving sequentially ammonium sulfate fractionation, heat treatment, anion exchange chromatography on DEAE-cellulose and gel filtration on Sephacryl S-200. Divalent cations (Mg²⁺ and/or Ca²⁺) were present throughout the purification which was entirely performed in the absence of chelators. The final yield was approx. 90 mg per kg testis. Ram testis calmodulin appears to be essentially identical to the brain homologous protein by the following criteria: ultraviolet absorption spectrum, amino acid composition showing a single residue of ?-N-trimethyl lysine, and tryptic peptide maps obtained by high performance liquid chromatography. Turkey gizzard myosin light-chain kinase, the activation of which is extremely specific for calmodulin (Walsh, M.P., Vallet, B., Cavadore, J.C. and Demaille, J.G. (1980) J. Biol. Chem. 255, 335–337), was indeed activated by ram testis calmodulin in the presence of calcium. The isolated protein migrated at different rates upon sodium dodecyl sulfate polyacrylamide gel electrophoresis, depending on the absence or presence of divalent metals which probably induce different conformations. The relative migration rates were Ca²⁺ > Mn²⁺ > Mg²⁺ > EDTA. In the presenceof divalent metals, the observed doublet may be ascribed to the equilibrium between ion-free and ion-saturated forms, which exhibited different Stokes radii, as already suggested (Grab, D.J., Berzins, K., Cohen, R.S. and Siekevitz, P. (1979) J. Biol. Chem. 254, 8690–8696).     

Concentration of L-phenylalanine with a reverse osmosis membrane

A high flux, thin film composite reverse osmosis (RO) membrane was used to concentrate L-phenylalanine (L-Phe) from clarified bioreactor harvest media. At pH 10±0.5 and 50°C, concentrations of 100 g l⁻¹ were easily achieved and at fluxes from 17 to 119 1 m⁻² h⁻¹. Rejection coefficient for L-Phe was inversely proportional (as the log) to retentate concentration. A preliminary system study showed that stages in a cascade could be used to recover essentially all of the product from clarified harvests. The study shows the importance of empirical evaluation as the basis of design and suggests that bioprocess applications of RO are likely to be case specific.     

Reminiscences,collaborations and reflections

This is a personal account by a semi old-timer who completed his official term as a professor of plant biochemistry at Nagoya University in Japan in 1992. My university student life began soon after the World War II (1948). I shared the hardships of many in my age group, in that life was difficult during my college years. I was fortunate to have the opportunity of studying in the USA on a Fulbright scholarship first at Purdue University (1955–1956), and then at the University of California, Berkeley (1956–1957). My graduate study and postdoctoral training in the new world were vitally refreshing and stimulating, which gave me the impetus for becoming a natural scientist associated with academic institutions. Consciously and subconsciously I was impressed by the friendly and liberal atmosphere surrounding young students as well as senior scholars in the United States. But more importantly, I was inspired by the critical and competitive minds prevailing among these people.The appointment as a biochemist at the International Rice Research Institute (IRRI) in the Philippines (1962–1964) was the real start of my professional career. The work was continued upon my return to Nagoya to become a staff member of the Research Institute for Biochemical Regulation (1964–1992). Throughout the years, my major research interest has covered photosynthesis as a whole, involving photosynthetic CO₂-fixation (RuBisCO), carbohydrate metabolism, e.g. starch biosynthesis and breakdown (-amylase), and metabolic regulation, which are interrelated in the basic metabolism of plant cells.I shall briefly describe in this article highlights from my studies and discoveries made and I shall also discuss their possible significance in plant metabolism, with the hope that it does not contradict my sense of humility: They are (a) discovery of ADPG in plants and its role in starch biosynthesis; (b) structure-function relationship of RuBisCO proteins, in particular on heterologous recombination of their subunits of plant-type enzyme molecules derived from the prokaryotic photosynthetic bacteria; (c) molecular evolution of RuBisCO genes; (d) mode of actions (formation, intracellular transport and secretion) of rice seed -amylase and its structural characteristics (distinctive glycosylation), and (e) DNA methylation and regulatory mechanism of photosynthesis gene expression in plastids (amyloplasts). In each step of my research, I shared joy, excitement, disappointment, and agony with my colleagues, an experience that may be common to all researchers. Although it is now becoming well recognized among the scientific community in Japan, I want to point out that interaction of multinational scientific minds in the laboratory produces a vital and creative atmosphere for performance of successful research. I experienced and realized this important fact in my earlier days in the USA and the Philippines. Inasmuch as I believe that this is the most crucial element for any research laboratory to possess, I fondly remember the friendships gained with numerous overseas visitors and collaborators who have contributed immensely to our work.Written at the invitation of Govindjee.     

Inducible nitric oxide synthase in innate immune cells is important for restricting cyst formation of Toxoplasma gondii in the brain but not required for the protective immune process to remove the cysts

Significantly larger numbers of Toxoplasma gondii cysts were detected in the brains of RAG1^?/?NOS2^?/? than RAG1^?/? mice following infection. In contrast, the cyst numbers markedly decreased in a same manner in both strains of mice after receiving CD8⁺ immune T cells. Thus, NOS2-mediated innate immunity is important for inhibiting formation of cysts in the brain but not required for the T cell-initiated cyst removal, which is associated with phagocyte accumulation. Treatment with chloroquine, an inhibitor of endolysosomal acidification, partially but significantly inhibited the T cell-mediated cyst removal, suggesting that phagosome–lysosome fusion could be involved in the T. gondii cyst elimination.     

SIRT6 对肝细胞脂质合成的影响及其转录基因分析

目的:在肝脏L-02 SIRT6-KO细胞系中,观察SIRT6在肝脏脂滴形成中的作用,初步研究在肝脏脂质代谢中SIRT6相关的转录差异基因发挥作用的分子机制。方法:利用基因敲除技术TALEN技术,构建肝脏L-02 SIRT6特异性敲除细胞系,并经q PCR和Western blot检测其表达水平;利用油酸刺激L-02 SIRT6-KO细胞及其对照组,体外模拟肝脏脂肪变的条件,并经高内涵和油红染色验证其脂滴形成能力;利用基因芯片检测L-02 SIRT6-KO及其对照细胞系中相关差异基因,并经生物信息学分析筛选脂代谢相关差异基因。结果:建立人肝脏SIRT6特异性敲除细胞系,q PCR显示m RNA下降50%,但Western blot证明SIRT6完全敲除;BODIPY实验及油红O染色发现,L-02 SIRT6-KO细胞比对照组其脂滴形成数量增多,高内涵荧光检测显示L-02 SIRT6-KO细胞中脂滴荧光强度比对照组增强(176.38±2.55 vs 104.26±2.08);通过对差异转录基因分析,发现了一组在脂质代谢中和SIRT6相关的关键基因如STEAP4、HMGA2、PDE1A、INSL4等。结论:成功建立人肝脏L-02 SIRT6-KO细胞系,并经实验证明SIRT6缺失能够促进脂滴形成;筛选到一组和SIRT6相关参与脂质代谢的关键基因。     

Epigenetic silencing of genes enhanced by collective role of reactive oxygen species and MAPK signaling downstream ERK/Snail axis: Ectopic application of hydrogen peroxide repress CDH1 gene by enhanced DNA methyltransferase activity in human breast cancer

Loss of E-cadherin and epithelial to mesenchymal transition (EMT) are key steps in cancer progression. Reactive oxygen species (ROS) play significant roles in cellular physiology and homeostasis. Roles of E-cadherin (CDH1), EMT and ROS are intriguingly illustrated in many cancers without focusing their collective concert during cancer progression. We report that hydrogen peroxide (H₂O₂) treatment modulate CDH1 gene expression by epigenetic modification(s). Sublethal dosage of H₂O₂ treatment decrease E-cadherin, increase DNMT1, HDAC1, Snail, Slug and enrich H3K9me3 and H3K27me3 in the CDH1 promoter. The effect of H₂O₂ was attenuated by ROS scavengers; NAC, lupeol and beta-sitosterol. DNMT inhibitor, AZA prevented the H₂O₂ induced promoter-CpG-island methylation of CDH1. Treatment of cells with U0126 (inhibitor of ERK) reduced the expression of DNMT1, Snail and Slug, increased CDH1. This implicates that CDH1 is synergistically repressed by histone methylation, DNA methylation and histone deacetylation mediated chromatin remodelling and activation of Snail and Slug through ERK pathway. Increased ROS leads to activation of epigenetic machineries and EMT activators Snail/Slug which in their course of action inactivates CDH1 gene and lack of E-cadherin protein promotes EMT in breast cancer cells. ROS and ERK signaling facilitate epigenetic silencing and support the fact that subtle increase of ROS above basal level act as key cell signaling molecules. Free radical scavengers, lupeol and beta-sitosterol may be tested for therapeutic intervention of breast cancer. This work broadens the amplitude of epigenome and open avenues for investigations on conjoint effects of canonical and intrinsic metabolite signaling and epigenetic modulations in cancer.     

Crystal structures of the substrate free-enzyme, and reaction intermediate of the HAD superfamily member, haloacid dehalogenase DehIVa from Burkholderia cepacia MBA4

DehIVa is a haloacid dehalogenase (EC 3.8.1.2) from the soil and water borne bacterium Burkholderia cepacia MBA4, which belongs to the functionally variable haloacid dehalogenase (HAD) superfamily of enzymes. The haloacid dehalogenases catalyse the removal of halides from haloacids resulting in a hydroxlated product. These enzymes are of interest for their potential to degrade recalcitrant halogenated environmental pollutants and their use in the synthesis of industrial chemicals. The haloacid dehalogenases utilise a nucleophilic attack on the substrate by an aspartic acid residue to form an enzyme-substrate ester bond and concomitantly cleaving of the carbon-halide bond and release of a hydroxylated product following ester hydrolysis. We present the crystal structures of both the substrate-free DehIVa refined to 1.93 A resolution and DehIVa covalently bound to l-2-monochloropropanoate trapped as a reaction intermediate, refined to 2.7 A resolution. Electron density consistent with a previously unidentified yet anticipated water molecule in the active site poised to donate its hydroxyl group to the product and its proton to the catalytic Asp11 is evident. It has been unclear how substrate enters the active site of this and related enzymes. The results of normal mode analysis (NMA) are presented and suggest a means whereby the predicted global dynamics of the enzyme allow for entry of the substrate into the active site. In the context of these results, the possible role of Arg42 and Asn178 in a "lock down" mechanism affecting active site access is discussed. In silico substrate docking of enantiomeric substrates has been examined in order to evaluate the enzymes enantioselectivity.     

Altered tyrosine metabolism and melanization complex formation underlie the developmental regulation of melanization in Manduca sexta

The study of hemolymph melanization in Lepidoptera has contributed greatly to our understanding of its role in insect immunity. Manduca sexta in particular has been an excellent model for identifying the myriad components of the phenoloxidase (PO) cascade and their activation through exposure to pathogen-associated molecular patterns (PAMPs). However, in a process that is not well characterized or understood, some insect species rapidly melanize upon wounding in the absence of added PAMPs. We sought to better understand this process by measuring wound-induced melanization in four insect species. Of these, only plasma from late 5th instar M. sexta was unable to melanize, even though each contained millimolar levels of the putative melanization substrate tyrosine (Tyr). Analysis of Tyr metabolism using substrate-free plasmas (SFPs) from late 5th instar larvae of each species showed that only M. sexta SFP failed to melanize with added Tyr. In contrast, early instar M. sexta larvae exhibited wound-induced melanization and Tyr metabolism, and SFPs prepared from these larvae melanized in the presence of Tyr. Early instar melanization in M. sexta was associated with the formation of a high mass protein complex that could be observed enzymatically in native gels or by PO-specific immunoblotting. Topical treatment of M. sexta larvae with the juvenile hormone (JH) analog methoprene delayed pupation and increased melanizing ability late in the instar, thus linking development with immunity. Our results demonstrate that melanization rates are highly variable in Lepidoptera, and that developmental stage can be an important factor for melanization within a species. More specifically, we show that the physiological substrate for melanization in M. sexta is Tyr, and that melanization is associated with the formation of a PO-containing protein complex.