Dissociation action of cationic peptides with hydrophobic radicals on functional coupling between serpentine type receptors and GTP-binding proteins

The coupling of hormone-activated receptor and heterotrimeric G protein is an important step of the signal transduction through adenylyl cyclase signal system (ACS). The numerous literature data and own results show that G protein-interacting regions, that are localized in cytoplasmic loops of receptors, have considerable positive charge, can form amphiphilic alpha-helices and are tightly associated with the membrane. We studied the influence of model cationic peptides on both basal and stimulated by hormones and nonhormonal agents adenylyl cyclase (AC) activity and on GTP binding activity of heterotrimeric G proteins in skeletal muscles of rats and smooth muscles of mollusc Anodonta cygnea. Peptides with hydrophobic radicals of caprinoyl acid (C10): Lys(C10)-His-Glu-Lys-Lys-(C10)-His-Glu-Lys-Lys(C10)-His-Glu-Lys-Lys(C10)- His-Glu-Lys-Ala-amide (peptide I), Cys-Lys(C10)-X-Tyr-Lys-Ala-Lys7-Trp-Lys-amide (II), Cys-X-Trp-Lys-Lys(C10)-Lys2-Lys(C10)-Lys3-Lys(C10)-Tyr-Lys-Lys(C10)-Lys-Lys- amide (III), where X--epsilon-aminocaproyl acid residue, were synthesized by solid-phase methodology. IC50 values for inhibiting the influence of peptides on serotonin-(molluscs) and isoproterenol-stimulated (rats) AC activity were: for peptide I--56 and 70 mkM, for peptide II--32 and 47 mkM, for peptide III--22 and 28 mkM, respectively. At the same time the peptides weakly decreased AC activity stimulated by nonhormonal agents (NaF, Gpp[NH]p, forskolin). Peptides I--III stimulated basal activity of the enzyme in both investigated tissues. The maximum stimulating effects (28--52%) of the peptides were observed at their concentration 10 mkM. Peptides (10--100 mkM) increased Gpp[NH]p binding in plasma membranes of mollusc and rat muscles and strongly decreased the influence of the hormones on the binding. Based on the obtained data we supposed that cationic peptides with hydrophobic radicals mimic G protein-binding regions of the receptors and can be involved in the regulation of functional coupling between the receptors and G proteins.     

SO2 污染油菜对桃蚜的影响

ＳＯ_２污染油菜对桃蚜的影响龚佩瑜,吴坤君,李秀珍（中国科学院动物研究所北京１０００８０）ＳＯ２是我国大气污染的主要成分,它是一种对生物影响很大的污染物。ｓｏ。曾被用作熏蒸剂来防治害虫,但只有在浓度很高时才有效。更多的观察表明,ｓｏ：污染有利于蚜虫的?..     

Active and passive properties of carotid arteries]

A mathematical model of carotid arteries is constructed from the known experimental data. Passive properties of the vascular wall are characterized by an alternating module of elasticity, the active ones by the specific power of muscle contraction. Its maximum value (0,023 n/m-3) is shown to be reached with intravascular pressure 190 mm Hg. The dependence of inner radius on the power of muscle contraction is studied at different values of intravascular pressure. It is shown that theactive properties of carotid arteries are essentially determined by their passive properties and depend on the stretching of the vessel wall.     

Polyphasic taxonomic analysis of <Emphasis Type="Italic">Bacillus</Emphasis> sp. strain C6—the antagonist of phytopathogenic microorganisms

Polyphasic taxonomic analysis was carried out for Bacillus sp. strain C6, as the antagonist of phytopathogenic bacteria and micromycetes. The combination of cultural, morphological, physiological, and biochemical properties of the strain has enabled researchers to refer it to the Bacillus subtilis group. It has been shown that the fatty acids of the strain’s cell walls were predominantly represented by branched iso- and anteiso-C15:0 and C17:0 fatty acids (over 85%), which was typical for the Bacillus amyloliquefaciens species. The molecular genetic analysis carried out on the nucleotide sequence of the 16S rRNA gene, and the profiling of polymorphic nucleotides have enabled researchers to refer the strain in question to Bacillus amyloliquefaciens subsp. plantarum.