DNA-Protein Complex in Circular DNA from Phage ϕ29

THE DNA of the B. subtilis phage ?29 has been described as unpermuted linear duplex molecules¹ of molecular weight 11 × 10⁶, but the formation of circular molecules has also been indicated, suggesting the existence of cohesive ends^1,2.     

Specificity and autoregulation of Notch binding by tandem WW domains in suppressor of Deltex

WW domains target proline-tyrosine (PY) motifs and frequently function as tandem pairs. When studied in isolation, single WW domains are notably promiscuous and regulatory mechanisms are undoubtedly required to ensure selective interactions. Here, we show that the fourth WW domain (WW4) of Suppressor of Deltex, a modular Nedd4-like protein that down-regulates the Notch receptor, is the primary mediator of a direct interaction with a Notch-PY motif. A natural Trp to Phe substitution in WW4 reduces its affinity for general PY sequences and enhances selective interaction with the Notch-PY motif via compensatory specificity-determining interactions with PY-flanking residues. When WW4 is paired with WW3, domain-domain association, impeding proper folding, competes with Notch-PY binding to WW4. This novel mode of autoinhibition is relieved by binding of another ligand to WW3. Such cooperativity may facilitate the transient regulatory interactions observed in vivo between Su(dx) and Notch in the endocytic pathway. The highly conserved tandem arrangement of WW domains in Nedd4 proteins, and similar arrangements in more diverse proteins, suggests domain-domain communication may be integral to regulation of their associated cellular activities.     

Thermoadaptation Characteristics of European River Lamprey Lampetra fluviatilis Smolts

Journal of Ichthyology - Thermoadaptation characteristics of smolts of European river lamprey Lampetra fluviatilis are studied in experimental conditions for the first time. The final preferred...     

The effect of the homogenates from different developmental stages of the nematode Protostrongylus rufescens (Leuckart, 1895) on mitochondrial and lipid bilayer membranes

The effect of the homogenates from different developmental stages of the nematode Protostrongylus rufescens on mitochondrial and lipid bilayer membranes has been studied. The homogenate of P. rufescens affects efficiently the cell energy by the inhibition of the mitochondrial respiration in the metabolic state V3, uncouples oxidative phosphorylation and affects the functions of mitochondria at the level of cyclosporine A-sensitive pore by making it highly permeable. Moreover, the nematode homogenate at the concentration of 1 mkg/ml increases efficiently the integral permeability of lipid bilayer membranes. An increase in this permeability is connected apparently with the formation of single ion channels. The channels of lipid bilayer membranes induced by the nematode homogenate show cation selectivity.     

Synthesis and antiviral activity of lupane triterpenoids with modified cycle E

A reductive transformation of the peroxide products of ozonolysis of derivatives of 3beta-O-acetyl-22(17-->28)-abeo-lupa-17(28),20(29)-diene and the subsequent intramolecular ketalization led to a compound with a trioxane fragment. This is a new approach to a skeletal modification of triterpenoid cycle E. An activity of the synthesized compounds was found toward the viruses of type A influenza and herpes simplex.     

Specific features of thermoregulation behavior in early juveniles of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> under thermogradient conditions

Specific features of thermoregulation behavior were studied, and values of the selected and final selected temperature (25.1°C) for early juveniles of roach Rutilus rutilus aged 11–28 days after hatching were first studied in long-term experiments (16 days). Two periods of the process of thermoselection—transient (selected temperature, up to 7–9 days after the beginning of the experiment) and final (final selected temperature, 8–10 days after the beginning of the experiment)—have been identified. The selection by larval roach of final selected temperature values occurs with use of the adaptation response of “excessive responding.” It was shown that correct determination of final selected temperature values for early juveniles of fish is possible only in long-term experiments (more than 7 days). The obtained results can be used during the analysis of behavior and distribution of larval roach under natural and experimental conditions.     

两个苜蓿品种营养器官解剖结构特征比较

为了明确具有极强抗虫特性的‘草原4号紫花苜蓿’(Medicago sativa L.‘Caoyuan No.4’) 营养器官的解剖特征,该研究选择具有抗蓟马特性较强的‘草原2号杂花苜蓿’(Medicago varia Martin.‘Caoyuan No.2’)为对照,采用显微镜观察比较两品种的根、茎、叶解剖结构特征,为揭示‘草原4号紫花苜蓿’ 抗蓟马特性提供理论依据。结果显示：(1)‘草原4号紫花苜蓿’根部解剖结构的皮层薄壁细胞厚度、内皮层厚度、形成层厚度、木质部厚度和木射线宽度等5个指标均极显著高于(P＜0.01)‘草原2号杂花苜蓿’,其中木射线宽度(159.37 μm)是‘草原2号杂花苜蓿’的1.82倍。(2)‘草原4号紫花苜蓿’的茎部厚角组织厚度(21.4 μm)极显著高于‘草原2号杂花苜蓿’(P＜0.01),而韧皮部宽度、髓直径却均极显著低于‘草原2号杂花苜蓿’(P＜0.01)。(3)‘草原4号紫花苜蓿’叶片解剖构造的7个指标均极显著高于‘草原2号杂花苜蓿’(P＜0.01),其中栅栏组织层数(2～3层)极明显地高于‘草原2号杂花苜蓿’(1~2层)。研究表明,‘草原4号紫花苜蓿’的组织结构特征具有明显的抗虫特征,且其组织的抗虫特征比‘草原2号杂花苜蓿’更为突出。     

A New Method to Characterize Hydrophobic Organization of Proteins: Application to Rational Protein Engineering of Barnase

Abstract

We present a new algorithm for characterization of protein spatial structure basing on the molecular hydrophobicity potential approach. The method is illustrated by the analysis of three-dimensional structure of barnase and barnase-barstar complex. Current approach enables identification of amino acid residues situated in unfavorable environment (these residues may be “active” for binding), and to map quantitatively hydrophobic, hydrophilic and unfavorable hydrophobic-hydrophilic intra-and inter-molecular contacts involving backbone and side-chain segments of amino acid residues. Calculation of individual contributions of amino acid residues to such contacts permits identification of structurally-important residues. The contact plots obtained with molecular hydrophobicity potential calculations, provide easy rules to choose sites for mutations, which can increase a strength of intra- or inter-molecular hydrophobic interactions. The unfavorable hydrophobic-hydrophilic contact can be mutated to favorable hydrophobic, and already existing weak hydrophobic contact can be strengthen by increasing hydrophobicity of residues in contact. Basing on the analysis of the contact plots, we suggest several mutations of barnase which are supposed to increase intramolecular hydrophobic interactions, and thus might lead to increased stability of the protein. Part of these mutations was studied previously experimentally, and indeed stabilized barnase. The other of predicted mutations were not studied experimentally yet. Several new mutations of barnase and barstar are also proposed to enhance the hydrophobic interactions on their binding interface.