Novel S-benzylisothiourea compound that induces spherical cells in Escherichia coli probably by acting on a rod-shape-determining protein(s) other than penicillin-binding protein 2

Random screening for inhibitors of chromosome partitioning in Escherichia coli was done by the anucleate cell blue assay. A novel S-benzylisothiourea derivative, S-(3,4-dichlorobenzyl)isothiourea, tentatively named A22, was found to induce spherical cells and spherical anucleate cells in E. coli. Mecillinam, a specific inhibitor of penicillin-binding protein 2, which induces spherical cells in E. coli, also caused anucleate cell production. Spherical cells induced by treatment with either A22 or mecillinam varied in size, and anucleate cells seemed to be more frequent among the smaller cells. These results suggest that loss of the rod shape in E. coli leads to asymmetric cell division that results in production of anucleate cells. No competition was observed even in the presence of a 10-fold excess A22 in an in vitro assay of 14C-penicillin G binding, but mecillinam specifically inhibited binding of 14C-penicillin G to penicillin-binding protein 2. Simultaneous treatment with mecillinam and cephalexin, a specific inhibitor of penicillin-binding protein 3, induced lysis of E. coli cells, but a combination of A22 and cephalexin did not. These results suggest that the target molecule(s) of A22 was not penicillin-binding protein 2. A22 may act on a rod-shape-determining protein(s) other than penicillin-binding protein 2, such as RodA or MreB.     

柞蚕滞育蛹的体液防卫反应

本文对柞蚕Antheraea pernyi滞育蛹体液防卫的某些特性做了报道。结果表明：(1)经注射大肠杆菌诱导6h后,体液中出现了抗菌活性物质。诱导7d后,抗菌活力达到峰值,15d后活力消失。用生理盐水诱导的反应较快,4d后达到峰值,10d后活力消失。(2)经大肠杆菌诱导后的体液对苏芸金杆菌、大肠杆菌、枯草杆菌及金黄葡萄球菌均有杀菌效应。在最初5min内杀菌效率较高。注射生理盐水诱导的体液较大肠杆菌诱导的杀菌效果低。(3)用昆虫病原菌苏芸金杆菌及非病原菌大肠杆菌作不同的诱导源,诱导1d后的体液对大肠杆菌的抗菌活力差别不显著,但对柞蚕蛹的生活力及发育有明显影响;用苏芸金杆菌诱导的柞蚕滞育蛹3d后死亡,用大肠杆菌诱导的蛹能正常羽化。(4)在一定范围内用不同剂量的大肠杆菌进行诱导,其抗菌活力不受影响,但超过一定限度,既使是非病原菌也可以突破昆虫的防卫功能。     

家蝇幼虫抗菌相关蛋白/多肽的诱导及抗菌活性分析

对家蝇Musca domestica 3龄幼虫进行针刺、带菌针刺、热激和超声4种处理,并于处理后不同时间分别收集提取家蝇幼虫体内耐热总蛋白,比浊法测定其抗菌活性,经逐步回归分析确定抗菌相关蛋白/多肽。结果表明,4种处理均能诱导家蝇幼虫产生抗菌物质,其中表观分子量为22 kD的蛋白对藤黄微球菌和大肠杆菌均有抗菌作用,50 kD,13 kD,26 kD,7 kD的蛋白抗菌活性具有专一性。还发现一种37 kD的蛋白对抗菌活性有负作用,推测它可能是促进细胞生长的物质。     

Novel S-Benzylisothiourea Compound That Induces Spherical Cells in Escherichia coli Probably by Acting on a Rod-shape-determining Protein(s) Other Than Penicillin-binding Protein 2

Random screening for inhibitors of chromosome partitioning in Escherichia coli was done by the anucleate cell blue assay. A novel S-benzylisothiourea derivative, S-(3,4-dichlorobenzyl)isothiourea, tentatively named A22, was found to induce spherical cells and spherical anucleate cells in E. coli. Mecillinam, a specific inhibitor of penicillin-binding protein 2, which induces spherical cells in E. coli, also caused anucleate cell production. Spherical cells induced by treatment with either A22 or mecillinam varied in size, and anucleate cells seemed to be more frequent among the smaller cells. These results suggest that loss of the rod shape in E. coli leads to asymmetric cell division that results in production of anucleate cells. No competition was observed even in the presence of a 10-fold excess A22 in an in vitro assay of ¹⁴C-penicillin G binding, but mecillinam specifically inhibited binding of ¹⁴C-penicillin G to penicillin-binding protein 2. Simultaneous treatment with mecillinam and cephalexin, a specific inhibitor of penicillin-binding protein 3, induced lysis of E. coli cells, but a combination of A22 and cephalexin did not. These results suggest that the target molecule(s) of A22 was not penicillin-binding protein 2. A22 may act on a rod-shape-determining protein(s) other than penicillin-binding protein 2, such as RodA or MreB.     

2-萘酸加单氧酶基因及NADH:黄素还原酶基因的克隆与分析

伯克霍尔德氏菌(Burkholderiasp.)JT1500对2-萘酸(2-naphthoate)生物降解的关键步骤之一是通过2-萘酸加单氧酶羟化2-萘酸生成1-羟基-2-萘酸(1-hydroxy-2-naphthoate)。在已确定2-萘酸加单氧酶基因及其功能的基础上对含有该基因的一个4.8kb长度的基因簇进行了克隆测序。该序列上含有4个可能的阅读框orfB、orfC、orfD、orfA。序列比对发现,orfA序列与JaponicumUSDA110和RalstoniaeutrophaHF39中的加单氧酶基因同源性较高,orfB序列与BordetllapertussisTohamaI、RalstoniasolanacearumGMI1000和BordetellabronchisepticaRB50等菌中的黄素还原酶基因有一定的同源性。酶活分析发现只含基因orfA的重组大肠杆菌SA细胞提取液有很低的加氧活性,含基因orfB的重组子SB细胞提取液没有加氧活性,但在反应体系中同时加入SA和SB的细胞提取液后,其加氧活性显著增强,包含片段orfB orfA的重组子SB A在黄素(FMN、FAD)存在的情况下也表现出很强的加氧活性;在厌氧条件下,能检测出SB细胞提取液的黄素还原活性。基于以上信息,认为2-萘酸加单氧酶基因簇含有两个重要的组分黄素还原酶基因(nmoB)和加单氧酶基因(nmoA)。2-萘酸加单氧酶Nmo羟化2-萘酸的过程为先由黄素还原酶(NmoB)在NADH存在的条件下将黄素(FMN、FAD)还原为还原型黄素(FMNH2、FADH2),然后加单氧酶(NmoA)利用还原型黄素和O2羟化底物2-萘酸,生成1-羟基-2-萘酸。NmoB是NmoA的偶联蛋白。     

Effects of Pro --> peptoid residue substitution on cell selectivity and mechanism of antibacterial action of tritrpticin-amide antimicrobial peptide

To investigate the effect of Pro --> peptoid residue substitution on cell selectivity and the mechanism of antibacterial action of Pro-containing beta-turn antimicrobial peptides, we synthesized tritrpticin-amide (TP, VRRFPWWWPFLRR-NH(2)) and its peptoid residue-substituted peptides in which two Pro residues at positions 5 and 9 are replaced with Nleu (Leu peptoid residue), Nphe (Phe peptoid residue), or Nlys (Lys peptoid residue). Peptides with Pro --> Nphe (TPf) or Pro --> Nleu substitution (TPl) retained antibacterial activity but had significantly higher toxicity to mammalian cells. In contrast, Pro --> Nlys substitution (TPk) increased the antibacterial activity but decreased the toxicity to mammalian cells. Tryptophan fluorescence studies indicated that the bacterial cell selectivity of TPk is closely correlated with a preferential interaction with negatively charged phospholipids. Interestingly, TPk was much less effective at depolarizing of the membrane potential of Staphylococus aureus and Escherichia coli spheroplasts and causing the leakage of a fluorescent dye entrapped within negatively charged vesicles. Furthermore, confocal laser-scanning microscopy showed that TPk effectively penetrated the membrane of both E. coli and S. aureus and accumulated in the cytoplasm, whereas TP and TPf did not penetrate the cell membrane but remained outside or on the cell membrane. These results suggest that the bactericidal action of TPk is due to inhibition of the intracellular components after penetration of the bacterial cell membrane. In addition, TPK with Lys substitution effectively depolarized the membrane potential of S. aureus and E. coli spheroplasts. TPK induced rapid and effective dye leakage from bacterial membrane-mimicking liposomes and did not penetrate the bacterial cell membranes. These results suggested that the ability of TPk to penetrate the bacterial cell membranes appears to involve the dual effects that are related to the increase in the positive charge and the peptide's backbone change by peptoid residue substitution. Collectively, our results showed that Pro --> Nlys substitution in Pro-containing beta-turn antimicrobial peptides is a promising strategy for the design of new short bacterial cell-selective antimicrobial peptides with intracellular mechanisms of action.     

Structure-activity relationship study of the bacterial actin-like protein MreB inhibitors: effects of substitution of benzyl group in S-benzylisothiourea

We comprehensively investigated the effects of substitution of the benzyl group in S-benzylisothiourea derivatives on antibacterial activity, because we found previously that some substitutions enhanced it. A 2,4-Cl2-derivative was found to be the most effective compound, it was stronger than the original one in Gram-negative rod shaped-bacteria such as Escherichia coli and Salmonella typhimurium.     

Antimicrobial characteristic of insoluble alkylpyridinium iodide

Insoluble and soluble alkylpyridinium iodides (C8 to C18) were synthesized. The insoluble agents were quaternized 4-vinylpyridine-divinylbenzene copolymers. The insoluble agent [C12(50)] that contained 50% divinylbenzene and had a C12 alkyl chain was selected as the most suitable insoluble agent. C12(50) showed poor durability of the antibacterial activity, but C12(50), which had lost the activity, was refreshed by washing with ethanol. This washing became ineffective after a few cycles of antibacterial treatment and refreshment. Such C12(50) recovered the activity upon 1.0 N NaOH treatment. The antibacterial activity of C12(50) depended on its surface area. It showed high antimicrobial activity against gram-positive bacteria and also showed activity against gram-negative bacteria and yeasts. But the activities of C12(50) and laurylpyridinium iodide solution were different against some microbes. The antibacterial activities of the agents were investigated against Escherichia coli and Micrococcus luteus under various conditions. The activity of C12(50) was higher at a higher temperature or at a lower cell concentration. The activity of C12(50) decreased on addition of NaCl, glucose, or bovine albumin to the cell suspension or in 0.01 M sodium-potassium phosphate buffer. C12(50) showed less activity when cells were mixed with dead cells or the supernatant of dead cells killed in an autoclave. The mode of action of the laurylpyridinium iodide solution against E. coli and M. luteus was similar to that of C12(50) except for the influence of E. coli cell concentration.     

Antimicrobial characteristic of insoluble alkylpyridinium iodide.

Insoluble and soluble alkylpyridinium iodides (C8 to C18) were synthesized. The insoluble agents were quaternized 4-vinylpyridine-divinylbenzene copolymers. The insoluble agent [C12(50)] that contained 50% divinylbenzene and had a C12 alkyl chain was selected as the most suitable insoluble agent. C12(50) showed poor durability of the antibacterial activity, but C12(50), which had lost the activity, was refreshed by washing with ethanol. This washing became ineffective after a few cycles of antibacterial treatment and refreshment. Such C12(50) recovered the activity upon 1.0 N NaOH treatment. The antibacterial activity of C12(50) depended on its surface area. It showed high antimicrobial activity against gram-positive bacteria and also showed activity against gram-negative bacteria and yeasts. But the activities of C12(50) and laurylpyridinium iodide solution were different against some microbes. The antibacterial activities of the agents were investigated against Escherichia coli and Micrococcus luteus under various conditions. The activity of C12(50) was higher at a higher temperature or at a lower cell concentration. The activity of C12(50) decreased on addition of NaCl, glucose, or bovine albumin to the cell suspension or in 0.01 M sodium-potassium phosphate buffer. C12(50) showed less activity when cells were mixed with dead cells or the supernatant of dead cells killed in an autoclave. The mode of action of the laurylpyridinium iodide solution against E. coli and M. luteus was similar to that of C12(50) except for the influence of E. coli cell concentration.     

白花除虫菊化学成分及其生物活性的研究

该研究应用柱层析法、薄层层析法和波谱法对白花除虫菊(Pyrethrum cinerariifolium)全株甲醇提取物进行分离纯化、结构鉴定,并分别采用 MTT 法、生物活性测定法和抑菌圈法测定所得化合物抗肿瘤、杀线虫和抑菌活性。结果表明：经波谱法鉴定化合物结构分别为 tulirinol (1),sesamin (2),β-cyclopyrethrosin (3)和3,5-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-7,8-dimethoxy-4H-1-benzopyran-4-one (4)。抗肿瘤活性显示化合物3对白血病细胞株 HL-60、肝癌细胞株 SMMC-7721、肺癌细胞株 A-549、乳腺癌细胞株 MCF-7和结肠癌细胞株SW480均表现出显著的抑制活性,其 IC50分别为3.800、2.890、2.930、4.600和5.160μmol?L-1;化合物1活性比3稍弱,其 IC50分别为5.020、10.760、12.310、12.310和12.250μmol?L-1;其中化合物3对各肿瘤细胞株 IC50值均小于顺铂。抗菌活性表明化合物3对大肠杆菌、蜡样芽孢杆菌、枯草芽孢杆菌和金黄色葡萄球菌均表现出明显的抑菌活性,且随着浓度增加活性逐渐增强,而化合物1和化合物2仅对部分菌株表现出微弱抑菌活性;杀线虫活性显示化合物3对秀丽隐杆线虫和全齿复活线虫均表现出显著的毒杀活性,且随着时间、浓度增加活性逐渐增强;而在同一时间点对秀丽隐杆线虫的毒杀活性强于全齿复活线虫。从白花除虫菊中分离所得4个化合物均为首次从该植株中发现,且首次报道了化合物3杀线虫和抑菌活性,值得进一步开发应用。     

Electron-transfer capacity of catechin derivatives and influence on the cell cycle and apoptosis in HT29 cells

Galloylated and nongalloylated catechin conjugates with cysteine derivatives have been synthesized and evaluated for their capacity to scavenge free radicals and to influence crucial functions (cell cycle, apoptosis) in HT29 colon carcinoma cells. We show that the nonphenolic part of the molecule modified the capacity of catechins to donate hydrogen atoms and to transfer electrons to free radicals. Nongalloylated derivatives did not significantly influence either the cell cycle or apoptosis. Among the galloylated species, 4beta-[S-(O-ethyl-cysteinyl)]epicatechin 3-O-gallate, which showed a high electron-transfer capacity (5 e- per molecule), arrested the cell cycle and induced apoptosis as expected for galloylated catechins such as tea (-)-epigallocatechin 3-O-gallate. 4beta-[S-(N-Acetyl-O-methyl-cysteinyl)]epicatechin 3-O-gallate, which showed the highest hydrogen-donating capacity (10 H per molecule) while keeping the electron-transfer capacity low (2.9 e- per molecule), did not trigger any significant apoptosis. The gallate moiety did not appear to be sufficient for the pro-apoptotic effect of the catechin derivatives in HT29 cells. Instead, a high electron-transfer capacity is more likely to be behind this effect. The use of stable radicals sensitive exclusively to electron transfer may help to design molecules with either preventive scavenging action (high hydrogen donation, low electron transfer) or therapeutic pro-apoptotic activity (high electron transfer).     

细菌诱导对昆虫细胞系NIH-SaPe-4生长与抗菌蛋白活性的影响

离体昆虫细胞系在昆虫免疫、抗菌肽及蛋白研究和药物开发方面具有较好的应用前景。该文对双翅目麻蝇科麻蝇成虫卵巢胚细胞系NIH-SaPe-4在藤黄微球菌诱导和非诱导条件下,细胞密度和活力的变化、诱导对细胞生长的影响、抗菌活性及其活性随时间的变化关系等进行了研究,并对所得抗菌蛋白进行了初步分离纯化和稳定性评估。结果表明,诱导使得细胞密度增长减缓,活力变弱。诱导和非诱导组细胞均可产生对3种革兰氏阳性菌具有抑菌活性的抗菌蛋白,其中对藤黄微球菌的抑菌活性最明显;诱导组细胞抗菌蛋白活性出现时间、稳定期抑菌活性均大于非诱导组,诱导菌消失一段时间后抗菌活性恢复到同等水平。抗菌蛋白具有酸碱稳定性和热稳定性。2组抗菌蛋白粗提液经凝胶、反相分离纯化后均得到一种60 kDa左右的抗菌蛋白,诱导组电泳后条带亮度大于非诱导组。该研究为昆虫细胞抗菌蛋白性质、分离纯化等研究奠定了科学基础。     

Role of bacterial ribosomes in barotolerance.

The effects of high hydrostatic pressures on protein synthesis by whole cells and cell free preparations of Escherichia coli, Pseudomonas fluorescens, and Pseudomonas bathycetes were determined. Actively growing cells of P. bathycetes and P. fluorescens were less sensitive than were E. coli cells. Protein synthesis by cell free preparations of E. coli and P. fluorescens showed the same extent of inhibition as their respective whole cell preparations, whereas cell free preparations of P. bathycetes showed a marked increase in pressure sensitivity over whole cells. Protein synthesis by hybrid protein synthesizing cell free preparations (the ribosomes from one organism and the S-100 supernatant fraction from another) demonstrated that response to high pressure is dependent on the source of the ribosome employed. A hybrid system containing E. coli ribosomes and P. fluorescens S-100 shows the same sensitivity to pressure as a homologous E. coli system, whereas a hybrid containing P. fluorescens ribosomes and E. coli S-100 shows the greater pressure tolerance characteristic of the P. fluorescens homologous system.     

Block versus random amphiphilic copolymers as antibacterial agents

We examined the antibacterial and hemolytic activities in a series of amphiphilic block and random copolymers of poly(vinyl ether) derivatives prepared by base-assisting living cationic polymerization. Block and random amphiphilic copolymers with similar monomer compositions showed the same level of activity against Escherichia coli . However, the block copolymers are much less hemolytic compared to the highly hemolytic random copolymers. These results indicate that the amphiphilic copolymer structure is a key determinant of activity. Furthermore, the block copolymers induced dye leakage from lipid vesicles consisting of E. coli -type lipids, but not mammalian lipids, while the random copolymers disrupted both types of vesicles. In addition, both copolymers displayed bactericidal and hemolytic activities at concentrations 1 or 2 orders of magnitude lower than their critical (intermolecular) aggregation concentrations (CACs), as determined by light scattering measurements. This suggests that polymer aggregation or macromolecular assembly is not a requisite for the antibacterial activity and selectivity against bacteria over human red blood cells (RBCs). We speculate that different single-chain conformations between the block and random copolymers play an important role in the antibacterial action and underlying antibacterial mechanisms.     

Poly(ethylene imine)s as Antimicrobial Agents with Selective Activity

We report the structure-activity relationship in the antimicrobial activity of linear and branched poly(ethylene imine)s (L- and B-PEIs) with a range of molecular weights (MWs) (500-12?000). Both L- and B-PEIs displayed enhanced activity against Staphylococcus aureus over Escherichia coli. Both B- and L-PEIs did not cause any significant permeabilization of E. coli cytoplasmic membrane. L-PEIs induced depolarization of S. aureus membrane although B-PEIs did not. The low MW B-PEIs caused little or no hemolysis while L-PEIs are hemolytic. The low MW B-PEIs are less cytotoxic to human HEp-2 cells than other PEIs. However, they induced significant cell viability reduction after 24 h incubation. The results presented here highlight the interplay between polymer size and structure on activity.     

Degradation of oxidatively denatured proteins in Escherichia coli

When exposed to oxidative stress, by oxygen radicals or H2O2, E. coli exhibited decreased growth, decreased protein synthesis, and dose-dependent increases in protein degradation. The quinone menadione induced proteolysis when cells were incubated in air, but was not effective when cells were incubated without oxygen. Anaerobically grown cells also exhibited significantly lower proteolytic capacity than did cells that were grown aerobically. Xanthine plus xanthine oxidase (which generate O2- and H2O2) caused a stimulation of proteolysis which was inhibitable by catalase, but not by superoxide dismutase: Indicating that H2O2 was responsible for the increased protein degradation. Indeed, H2O2 alone was effective in inducing increased intracellular proteolysis. Two-dimensional polyacrylamide gel electrophoresis of [3H]leucine labeled E. coli revealed greater than 50% decreases in the concentrations of 10-15 cell proteins following H2O2 or menadione exposure, while several other proteins were less severely affected. To test for the presence of soluble proteases, we prepared cell-free extracts of E. coli and incubated them with radio-labeled protein substrates. E. coli extracts degraded casein and globin polypeptides at rapid rates but showed little activity with native proteins such as superoxide dismutase, hemoglobin, bovine serum albumin, or catalase. When these same proteins were denatured by exposure to oxygen radicals or H2O2, however, they became excellent substrates for degradation in E. coli extracts. Studies with albumin revealed correlations greater than 0.95 between the degree of oxidative denaturation and proteolytic susceptibility. Pretreatment of E. coli with menadione or H2O2 did not increase the proteolytic capacity of cell extracts; indicating that neither protease activation, nor protease induction were required.(ABSTRACT TRUNCATED AT 250 WORDS)     

A novel human hepatoma cell line, FLC-4, exhibits highly enhanced liver differentiation functions through the three-dimensional cell shape

We characterized three-dimensional human hepatoma cell lines, functional liver cell (FLC) cell lines, to establish a highly differentiated hepatoma cell line. We investigated the effect of extracellular matrix and cell morphology on liver-specific gene expression in FLC cells. The hepatocyte nuclear factor-4α (HNF-4α) and other liver-specific gene expressions were enhanced in spherical FLC-4 cells on EHS-gel, but other human hepatoma cells such as HepG2 did not show the enhancement. Importantly, the liver-specific gene expression levels in spherical FLC-4 cells cultured on EHS-gel were comparable to those of human liver and were much higher than those of other human hepatoma cell lines. The major matrix components and growth factors in EHS-gel did not affect cell shape and liver functions. To exclude any effect of the extracellular matrix, we made spherical FLC-4 cells by actin filament disruption. The actin-disrupted spherical cells also showed an enhanced liver-specific gene expression. We concluded that three-dimensional cell shape per se is one of the most important determinants of liver differentiation functions in FLC-4 cells. Cell morphology-dependent induction of liver-specific gene expression was mediated through microtubule organization. In conclusion, differentiation of FLC-4 human hepatoma cell line can be enhanced to a human liver-like level through the three-dimensional cell shape in a microtubule-dependent manner.     

A 4-aminofurazan derivative-A189-inhibits assembly of bacterial cell division protein FtsZ in vitro and in vivo

Out of 95,000 commercially available chemical compounds screened by the anucleate cell blue assay, 138 selected hit compounds were further screened. As a result, A189, a 4-aminofurazan derivative was found to inhibit FtsZ GTPase with an IC(50) of 80 mug/ml and to exhibit antibacterial activity against Staphylococcus aureus and Escherichia coli. Light scattering demonstrated that A189 inhibited FtsZ assembly in vitro, and microscopic observation of A189-treated E. coli indicated that A189 perturbed FtsZ ring formation and made bacterial cells filamentous. However, nucleoids staining with DAPI revealed that A189 did not affect DNA replication and chromosome segregation in bacterial filamentous cells. Furthermore, A189 made sulA-deleted E. coli cells filamentous. Taken together, these findings suggest that A189 inhibits FtsZ GTPase activity, resulting in perturbation of FtsZ ring formation, which leads to bacterial cell death.