RESUMEN
The distribution of secondary structures along the polypeptide chains of spider proteins spidroins 1 and 2 and their recombinant analogs has been studied by statistical methods. It was found that these proteins in the monomolecular form contain only trace amounts of beta-structures. At the same time, the regions of the sequence including Ala and Gly are predicted as helical-containing (with alpha-helices and left-helices of polyproline II type). An analysis of literature data and our data obtained in this study shows that the main conformation of the polypeptide chain solutions of spidroins 1 and 2 and their recombinant analogs in water solutions is the left-helix of polyproline II type with some contaminations of alpha-helices and a very small share of beta-structures. The transition to the state with extended conformations, which are peculiar to mature filaments of spider webs, requires the dehydration of the polypeptide chain backbone. Thus, the genesis of beta-structure in spider web proteins is determined by the conditions of conformation transitions between the main regular conformations of the polypeptide chain backbone.
Asunto(s)
Fibroínas/química , Péptidos/química , Arañas , Secuencia de Aminoácidos , Animales , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , Proteínas Recombinantes/químicaAsunto(s)
Proteínas Bacterianas/metabolismo , Endorribonucleasas/metabolismo , Ribonucleasas/metabolismo , Proteínas Bacterianas/genética , Rastreo Diferencial de Calorimetría , Dicroismo Circular , Endorribonucleasas/química , Calor , Modelos Moleculares , Mutación , Unión Proteica , Desnaturalización Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Ribonucleasas/químicaAsunto(s)
Endorribonucleasas/química , Ribonucleasas/química , Proteínas Bacterianas , Rastreo Diferencial de Calorimetría , Dicroismo Circular , Endorribonucleasas/genética , Concentración de Iones de Hidrógeno , Conformación Proteica , Desnaturalización Proteica , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Ribonucleasas/genética , TermodinámicaRESUMEN
The effect of ethanol and medium pH on thermodynamic parameters and cooperativity of pepsinogen thermal denaturation have been studied by scanning microcalorimetry. Addition of 20% (v/v) ethanol decreases the protein temperature of denaturation by 10.7 degrees C at pH 6.4 and by 15.8 degrees C at pH 8.0. It decreases the denaturation heat capacity change of pepsinogen from 5.8 to 4.2 kcal/K.mol, but has no effect on the number of energetic domains (regions melting in an "all-or-none" manner). The dependences of calorimetric denaturation enthalpy on denaturation temperature in both aqueous solution and 20% ethanol are linear and converge at about 95 degrees C, which coincides with the converge temperature of similar dependencies shown for a number of proteins in aqueous and water-alcohol solutions. A change of pH from 5.9 to 8.2 in 20% ethanol has been shown to cause a decrease of the number of cooperatively melting regions in pepsinogen. This process involves no changes either in the secondary structure or in the local surroundings of aromatic amino acids. It is concluded that ethanol addition has no effect on pepsinogen denaturation cooperativity until there is sufficient influence on intramolecular charge distribution, taking place upon a change of pH.
Asunto(s)
Etanol/farmacología , Pepsinógenos/química , Animales , Rastreo Diferencial de Calorimetría , Dicroismo Circular , Activación Enzimática , Calor , Concentración de Iones de Hidrógeno , Pepsina A/metabolismo , Pepsinógenos/metabolismo , Desnaturalización Proteica , Estructura Secundaria de Proteína , Porcinos , TermodinámicaRESUMEN
Circular dichroism technique has been used for investigating the conformation of histone H1 and H5 C-terminal fragments and beta-endorphin. It has been shown that in aqueous solution these polypeptides adopt preferably the left-handed helical conformation of the poly-L-proline II type. The linear temperature dependence of the CD value during solution heating was found to be broken in the temperature interval between 50 and 55 degrees C. It was supposed to occur due to the conformation destruction.
Asunto(s)
Histonas/química , Fragmentos de Péptidos/química , betaendorfina/química , Secuencia de Aminoácidos , Animales , Bovinos , Pollos , Dicroismo Circular , Calor , Datos de Secuencia Molecular , Conformación Proteica , PorcinosRESUMEN
The conformation of human growth hormone (hGH) as monomer and aggregate as well as of those immobilized in the soluble polysaccharide matrix was investigated. The immobilization resulted in ten per cent decrease of the amount of alpha-helix and in the conformational mobility change of aromatic amino acid side groups. It did not, however, influence the biological activity of the hormone, thus suggesting that the above conformational variations did not affect functionally important portions of the molecule.
Asunto(s)
Hormona del Crecimiento , Dicroismo Circular , Humanos , Conformación ProteicaRESUMEN
Method of scanning calorimetry of intact and denervated F-actin shows a change in thermostability of protein after denervation.
Asunto(s)
Actinas/análisis , Desnervación Muscular , Músculos/análisis , Animales , Rastreo Diferencial de Calorimetría , ConejosRESUMEN
The damaging effects on the structure of a supramolecular DNA complex of sarcoma-37 cells in mice following the use of the therapeutic doses of khanerol were found. Capillary elastoviscosimetry and nucleoid sedimentation procedure showed that the damage of the supramolecular DNA complex structure becomes apparent already after 4 hours, and increases by 24 hour. In studies of the binding of khanerol with DNA by Cd and Tmelt. the procedure showed direct interaction of khanerol with DNA. The role of conformational changes of the supramolecular DNA complex in the cytotoxic action of antitumour agents is discussed.
Asunto(s)
Antineoplásicos Fitogénicos/uso terapéutico , ADN de Neoplasias/efectos de los fármacos , ADN Superhelicoidal/efectos de los fármacos , Sarcoma 37/tratamiento farmacológico , Sarcoma Experimental/tratamiento farmacológico , Animales , Dicroismo Circular , Evaluación Preclínica de Medicamentos , Interacciones Farmacológicas , Ratones , Ratones Endogámicos , Trasplante de Neoplasias , Fenoles , Sarcoma 37/genética , Factores de Tiempo , ViscosidadRESUMEN
Method of circular dichroism did not indicate any changes of the secondary structure of globular and fibrillar actin from denervated skeletal muscles. The matter that some conformational changes of the aromatic residues do in fact accompany denervation was confirmed by fluorescence studies but not by CD spectra.
Asunto(s)
Actinas/análisis , Desnervación Muscular , Músculos/análisis , Animales , Dicroismo Circular , ConejosRESUMEN
For the first time the individual positive circular dichroism peaks at 268 nm, 262 nm and 256 nm have been found for collagen. These peaks are due to the vibronic nature of a weak pi-pi* phenylic chromophore transition of phenylalanine and the unique structural organization of collagen where water molecules are an essential element of the triple helix.
Asunto(s)
Colágeno/análisis , Fenilalanina , Piel/análisis , Animales , Dicroismo Circular , Peces , RatasRESUMEN
The spectral criterion of a left-handed helix of the poly-L-proline II type was elaborated during the study of a number of synthesized oligopeptides (in a solid state and solution): (Gly-Pro-Pro)1-8, (Gly-Pro)1, (Gly-Pro-Ala)1-4, (Gly-Pro-Gly)1-4, (Gly-Pro-Pro) X (Gly-Pro-Gly)1-2(Gly-Pro-Pro), (Gly-Pro-Pro)n, (Orn3-Gly)n and also rat skin collagen by X-ray diffraction, circular dichroism and infrared spectroscopy methods; the characteristic shape of the left-handed helix CD spectrum was found. The change of spectral characteristics with the change of left-handed helix distortion was established. The linear noncooperative melting process of the left-handed conformation was demonstrated. The data obtained allow to determine qualitatively the presence of the left-handed helix in different polypeptides and proteins.
Asunto(s)
Colágeno , Péptidos , Animales , Dicroismo Circular , Conformación Proteica , Ratas , Piel , Espectrofotometría Infrarroja , Estereoisomerismo , Difracción de Rayos XRESUMEN
Transition from B to A form of DNA in water/ethanol solutions is hindered by stoichiometric quantities of a bifunctional cation, bis-(2-guanidoethyl)disulfide (GED). Using the data on the shift and widening of the B--A transition curves in the presence of GED, a value of the order of 10 base pairs has been estimated for the cooperativity length of the B--A transition which agrees well with the values earlier obtained.
Asunto(s)
ADN , Guanidinas , Conformación de Ácido Nucleico , Animales , Bovinos , Cinética , TimoRESUMEN
The specificity of the secondary structure of a number of polypeptide hormones of the pituitary gland anterior lobe and their fragments were studied by circular dichroism method in the peptide bond absorption region and infrared spectroscopy. The state of objects had been examined in solvents of different polarity in a wide temperature range. The polypeptide chain of a greater part of hormones in aqueous solution is shown to represent a left-handed helix of the poly-L-proline II type. The reversible melting process of the left-handed conformation when heated in aqueous solution appears to be non-cooperative: delta epsilon is linearly dependent on temperature. Upon temperature lowering the left-handed structure is stabilized, its defects decrease. The mode of transition from the left-handed form to the alpha- and the beta-forms in organic solvents was followed. Contributions of peptide chromophores and those of aromatic amino acid side group chromophores with circular dichroism bands in regions under study were differentiated upon analysis of circular dichroism spectra. The data obtained allow to correlate conformation of separate fragments in the hormone chain with functional activity.
Asunto(s)
Hormonas Adenohipofisarias , Animales , Dicroismo Circular , Conformación Proteica , Solventes , Porcinos , TemperaturaRESUMEN
Earlier we have shown that DNA forms stoichiometric complexes with bis-(2-guanidoethyl)-disulfide (GED), the helix being transformed from the B-like structure into the C-like one. The present work demonstrates that the DNA helix in the saturated complex does not change its conformation within a broad range of conditions: 0 less than [NaCl] less than 5.10(-2) M; 0% less than [methanol] less than 60% (v/v); 5 degrees less than temperature less than 50 degrees. Free DNA undergoes a non-cooperative winding within the B-family under all these influences. Increase in NaCl concentration beyond 5.10(-2) M results in abrupt cooperative unwinding from the C-like form to the B-like one, apparently due to GED dissociation. The obtained data are in accord with the idea that the conformational transition of DNA within the B-family is induced by change of phosphates interaction with the hydrated cations of alcaline metals; formation of strong hydrogen bonds of the phosphates with GED makes the DNA helix non-sensitive to variations of the environment.
Asunto(s)
ADN , Disulfuros , Guanidinas , Cinética , Metanol , Desnaturalización de Ácido Nucleico , Concentración Osmolar , Cloruro de SodioRESUMEN
Circular dichroism (CD) and infrared spectroscopy (IRS) studies of aqueous solutions of fourth N-terminal peptides of histone H4 with different chain length were carried out under various conditions. It was shown that all studied peptides had conformation of extended left-handed helix as well as poly-1-proline II at the acidic and neutral pH, in moderate ionic strength (0,15), in 80% ethanol, 0,2 M sodium dodecylsulphate, in 8 M urea and 5 M guanidinum hydrochloride. This conformation was changed by raising temperature, under transition to the range of basic pH and in the concentrated solutions of CaCl2 (5M).
Asunto(s)
Histonas , Secuencia de Aminoácidos , Fenómenos Químicos , Química , Dicroismo Circular , Modelos Químicos , Oligopéptidos , Conformación Proteica , Espectrofotometría InfrarrojaRESUMEN
Addition of the bifunctional cations, bis(2-aminoethyl) disulphide-cystamine, and bis(2-guanidoethyl) disulphide-GED, into water solution of DNA results in a decrease in magnitude of the positive circular dichroism (CD) band. However, unlike the similar effect due to alcaline ions or ions of ammonium and guanidinium the above effect occurs at much smaller, stoichiometric with phosphates, concentrations of the dications. Another peculiarity of GED is the attaining of a plato region for the curve of the CD change with the rise of GED concentration. Since the decrease in positive band CD is connected with increase in the rotation angle between the base pairs, the observed behavior of the bifunctional cations are supposedly due to peculiarities of their winding action upon DNA helix. Reducing the disulphide bond in the cations gives rise to increase in the DNA positive CD band up to the values inherent to those in the presence of the corresponding monocations. The higher efficiency of the bifunctional cations is thus due to the cationic groups belong to one and the same molecule. Such compounds could thus be considered as a simple model of DNA-protein interaction.
Asunto(s)
ADN Bacteriano , Amoníaco , Cationes Bivalentes , Dicroismo Circular , Cistamina , Disulfuros , Escherichia coli , Guanidinas , Conformación de Ácido NucleicoRESUMEN
By circular dichroism method the nature of the secondary structure of owine and bovine adrenocroticotropic hormone in water has been studied. An analysis of circular dichrosim spectra and their dependence on temperature point to a left-helical conformation (of the poly-L-proline II type) of the polypeptide chain of adrenocorticopic hormone in water.
Asunto(s)
Hormona Adrenocorticotrópica , Animales , Bovinos , Dicroismo Circular , Conformación Molecular , Soluciones , Porcinos , AguaRESUMEN
Structural features of porcine and bovine beta-lipotropic hormone and fragments of porcine hormone have been studied by the methods of circular dichroism and infra-red sectroscopy and by analysis of amino acid sequence. It has been established that the structure of the hormone includes a set of regular helical forms which varies considerably with the humidity and dielectric constant of the medium. The presence of left-handed helical conformations of the poly-L-proline II type in aqueous medium and moist films and their transformations with the variation of the parameters of the medium has been demonstrated. The role of the extended left-handed helical structures in hormone functions in the blood and intercellular space is discussed.