都匀楼梯草 贵州荨麻科一新种

描述了在中国贵州发现的楼梯草属一新种:都匀楼梯草Elatostema duyunense W.T.Wang&Y.G.Wei,本种在亲缘关系上与上林楼梯草E.shanglinense W.T.Wang甚为相近,但根状茎细长,明显,茎较高,叶上面近牙齿顶端处被极短糙伏毛,托叶较大,条形或宽条形,有1条褐色脉,雄花序有短梗,花序托近圆形,明显,苞片6,其中2枚较大,卵状三角形,4枚较小,船状条形,小苞片无毛而与后者不同。     

Argonaute亚族蛋白对人类肿瘤细胞周期的影响

Argonaute(Ago)家族蛋白与小的非编码RNAs(siRNAs, miRNAs, piRNAs)生物发生和细胞功能密切相关．它可以结合小RNAs,调控蛋白质的合成或影响mRNA的稳定性,即RNA干扰(RNAi),并且参与Piwi相关RNAs(piRNAs)的生成．人类Argonaute蛋白家族包括8个成员,对其中的4个(Ago1～Ago4)mRNAs进行了实时定量PCR(qRT-PCR)检测,其在许多细胞中共表达,与细胞生长紧密相关．针对人乳腺癌MCF7和子宫颈癌HeLa细胞系,通过下调Ago亚族蛋白表达量,研究其在细胞周期中的调控作用．MTT实验证明,Ago蛋白表达缺失导致细胞增殖活性显著下降(P < 0.01),生长受阻．进一步研究揭示,细胞周期在G0/G1期发生停滞,其中Ago1(P < 0.01)和Ago4(P < 0.05)的作用尤为明显,但并不引发凋亡．虽然具体调控机制尚不清晰,但在人类肿瘤细胞中Argonaute蛋白可直接或间接地参与细胞周期进程的调控．     

Efficient production of membrane-integrated and detergent-soluble G protein-coupled receptors in Escherichia coli

G protein-coupled receptors (GPCRs) are notoriously difficult to express, particularly in microbial systems. Using GPCR fusions with the green fluorescent protein (GFP), we conducted studies to identify bacterial host effector genes that result in a general and significant enhancement in the amount of membrane-integrated human GPCRs that can be produced in Escherichia coli. We show that coexpression of the membrane-bound AAA+ protease FtsH greatly enhances the expression yield of four different class I GPCRs, irrespective of the presence of GFP. Using this new expression system, we produced 0.5 and 2 mg/L of detergent-solubilized and purified full-length central cannabinoid receptor (CB1) and bradykinin receptor 2 (BR2) in shake flask cultures, respectively, two proteins that had previously eluded expression in microbial systems.     

Generation and characterization of human monoclonal antibodies to G5, a linear neutralization epitope on glycoprotein of rabies virus, by phage display technology

The aim of the present study was to discover distinct human MAbs to RV with high neutralizing potency and a broad neutralization spectrum. A phage display technology was used to produce human scFv to G5, a conserved linear neutralization epitope on Gp of RV. A phage display scFv library with 6 x 10(7) members was constructed and the phage-scFv with 'antigen-binding' activities were selected with synthetic peptide G5-24. The obtained scFv genes were cloned into pET22b(+)/BL21(DE3) and from this we prepared purified scFv fragments. The assay of the specificity characteristics and neutralization capacity showed that two distinct clones with new human immunoglobulin V genes can recognize G5 specifically as well as neutralize different RV strains. They have potential for inclusion in an antibodies combination aimed for use in rabies PEP.     

Palmitate and oleate induction of acylation stimulating protein resistance in 3T3-L1 adipocytes and preadipocytes

Acylation stimulating protein (ASP) stimulates triglyceride synthesis and glucose transport via its receptor C5L2. The aims were (i) to evaluate ASP response under insulin-resistant conditions and (ii) to identify mechanisms of ASP resistance using 3T3-L1 adipocytes and preadipocytes. Overnight incubation with palmitate (PAL) or oleate (OLE) induced dose-dependent inhibition of ASP-stimulated glucose transport in adipocytes (198 +/- 18% +ASP, 100 +/- 4% basal, 131 +/- 14% + ASP + 1 mmol/L PAL) and preadipocytes (287 +/- 21% + ASP, 100 +/- 4% basal, 109 +/- 13% + ASP + 1 mmol/L PAL). In adipocytes, dose-dependent maximal C5L2 mRNA decreases were -41 +/- 15% and -82 +/- 2%, with decreased cell-surface C5L2 of -55 +/- 12% and -39 +/- 9% (1 mmol/L PAL and OLE, respectively) with no change in preadipocytes. Adipocytes treated with PAL or OLE evidenced inhibition of ASP stimulation of G proteins: Gbeta (-50%), Galphaq/11 (-50%) and protein kinase C: PKCalpha-P (-52%), PKCzeta-P (-43%). Fatty acid-induced ASP resistance via C5L2 may contribute to altered adipose tissue function and obesity/insulin resistance phenotype in humans.     

A mathematically related singularity and the maximum size of protein domains

In a paper titled "A topologically related singularity suggests a maximum preferred size for protein domains" (Zbilut et al., Proteins 2007;66:621-629), Zbilut et al. claim to have found a singularity in certain geometrical properties of protein structures, and suggest that this singularity may limit the maximum size of protein domains. They find further support for the singularity in their analysis of G-factors calculated by the PROCHECK program. Here, we show that the claimed singularity is a mathematical artifact with no physical meaning, and we reanalyze the G-factors to show that Zbilut et al.'s results are due to a single outlier in the data. Thus, the existence of an actual singularity in the topological properties of proteins is not supported by the findings of Zbilut et al.     

Expanding GPCR homology model binding sites via a balloon potential: A molecular dynamics refinement approach

Homology modeling of G protein-coupled receptors is becoming a widely used tool in drug discovery. However, unrefined models built using the bovine rhodopsin crystal structure as the template, often have binding sites that are too small to accommodate known ligands. Here, we present a novel systematic method to refine model active sites based on a pressure-guided molecular dynamics simulation. A distinct advantage of this approach is the ability to introduce systematic perturbations in model backbone atoms in addition to side chain adjustments. The method is validated on two test cases: (1) docking of retinal into an MD-relaxed structure of opsin and (2) docking of known ligands into a homology model of the CCR2 receptor. In both cases, we show that the MD expansion algorithm makes it possible to dock the ligands in poses that agree with the crystal structure or mutagenesis data.     

Unfolding energetics and stability of banana lectin

The unfolding pathway of banana lectin from Musa paradisiaca was determined by isothermal denaturation induced by the chaotrope GdnCl. The unfolding was found to be a reversible process. The data obtained by isothermal denaturation provided information on conformational stability of banana lectin. The high values of DeltaG of unfolding at various temperatures indicated the strength of intersubunit interactions. It was found that banana lectin is a very stable and denatures at high chaotrope concentrations only. The basis of the stability may be attributed to strong hydrogen bonds of the order 2.5-3.1 A at the dimeric interface along with the presence of water bridges. This is perhaps very unique example in proteins where subunit association is not a consequence of the predominance of hydrophobic interactions.     

UDP-glucose:(6-methoxy)podophyllotoxin 7-O-glucosyltransferase from suspension cultures of Linum nodiflorum

Cell cultures of Linum species store 6-methoxypodophyllotoxin (MPTOX), podophyllotoxin (PTOX) and related lignans as O-glucosides. UDP-glucose:(M)PTOX 7-O-glucosyltransferase has been detected and characterised in protein preparations of suspension-cultured cells of Linum nodiflorum L. (Linaceae). The maximal lignan glucoside contents in the cells are preceded by a rapid increase of the specific glucosyltransferase activity on day six of the culture period. MPTOX glucoside is the major lignan with up to 1.18 mg g(-1) of the cell dry wt which is more than 30-fold of the PTOX glucoside content. Of the three aryltetralin lignans tested as substrates, PTOX and MPTOX display comparable apparent K(m) values of 4.7 and 5.4 microM, respectively. 5'-Demethoxy-6-methoxypodophyllotoxin is converted with the highest velocity of 25.2 pkat mg(-1) while also possessing a higher K(m) of 14.7 microM. Two-substrate test series indicate that all three compounds compete for the active site of a single protein. The structurally similar lignan beta-peltatin acts as competitive inhibitor as well. However, the 6-O-glucosidation is most likely catalysed by a separate enzyme. The (M)PTOX 7-O-glucosyltransferase works best at a pH around 9 and a temperature around 35 degrees C. A 15-30% increase of the reaction rate is effected by the addition of 0.9 mM Mn(2+).