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A Cavaggioni

Publications and source records attributed to A Cavaggioni.

At least 37 records · Page 2Linked to original sources
PubMed1989

Complete amino acid sequence of pyrazine-binding protein from cow nasal mucosa.

The sequence is reported of the pyrazine-binding protein from cow olfactory/respiratory mucosa. The protein consists of 159 amino acids and clearly belongs to the retinol-binding protein family. It is most closely related to the urinary proteins from mice and rats and to the odour-binding protein from rat nasal epithelium. It is unique however, in that only one of the otherwise conserved features of the family is still present--namely a single tryptophan. Most surprisingly the protein contains no cysteine and, therefore, does not rely for its structural stability on the disulphide bond(s) present in other members of this group. A model for the protein has been constructed based on the co-ordinates of beta-lactoglobulin. From this, it is possible to identify residues which may line the binding site. The impression gained is of a much larger pocket than occurs with retinol-binding protein or beta-lactoglobulin. The character of the binding pocket remains essentially hydrophobic but with a significant reduction in its aromatic content and an increase in H-bonding side chains.

Amino Acid Sequence↗
PubMed1988

Regulation of cyclic GMP binding to retinal rod membranes by calcium.

The apparently cooperative binding of 8-(5-thioacetamidofluorescein)-cGMP (SAF-cGMP) to cGMP-binding sites of the rod outer segments is regulated by Ca2+ in the 0.1-1 microM activity range. High Ca2+ reduces, and low Ca2+ increases the affinity of SAF-cGMP binding. This regulation involves only intrinsic membrane components. It is proposed that an allosteric regulation of cGMP binding by Ca2+ can contribute to photoreceptor potential adaptation.

Animals↗
PubMed1988

The pyrazine-binding protein and olfaction.

1. The present results provide circumstantial evidence, but not a proof, that the Pyrazine-binding Protein is an odorant carrier molecule of fundamental importance. 2. At first sight a role for a secretory protein in olfaction is not obvious. 3. Odorants freely diffuse in air, in water and in lipids, and the use of carrier proteins, would seem superfluous unless a very special combination with the odorant occurs [Gaupp E. (1902) In Anatomie des Frosches, 2nd Edn, pp. 673. Vieweg-Verlag, Braunschweig]. 4. The possibility should be considered that the Pyrazine-binding Protein and the urinary proteins belong to a large family of species-specific secretory molecules which, with the odorant bound, directly stimulate the receptor cell.

Animals↗
PubMed1987

Homology between the pyrazine-binding protein from nasal mucosa and major urinary proteins.

Sequence analysis of the pyrazine-binding protein from bovine olfactory mucosa reveals marked homology with a family of proteins of unknown function found in the urine of the adult male mouse and rat. In view of the dramatic biological responses to odorants transmitted in male rodent urines, it is proposed that these proteins play important roles in some aspects of odor transmission and reception.

Amino Acid Sequence↗
PubMed1987

Immunocytochemical localization of pyrazine-binding protein in bovine nasal mucosa.

Polyclonal antibodies have been raised against purified bovine pyrazine-binding protein, a protein that binds the odorant 2-isobutyl-3-methoxypyrazine. These antibodies have been utilized in immunocytochemical experiments to localize the pyrazine-binding protein in bovine nasal mucosa. Tissue fragments, macroscopically identified as olfactory and respiratory mucosa, were fixed in Bouin's fluid and embedded in paraffin. Consecutive serial sections were processed for immunofluorescence studies and restained either with haematoxylin-eosin or with periodic acid Schiff-Alcian Blue. In both olfactory and respiratory mucosa, only seromucous tubulo-acinar glands were specifically labelled. These glands are located in the lamina propria underlying typical respiratory epithelium, even in those tissues that are macroscopically defined as olfactory mucosa.

Animals↗
PubMed1985

Binding stoichiometry of a fluorescent cGMP analogue to membranes of retinal rod outer segments.

The high-affinity binding of the cGMP analogue 8-(5-thioacetamidofluorescein)-cGMP to rod outer segment membranes depleted of peripherally bound proteins has been defined by equilibrium dialysis (mean +/- SD): membranes contain about one cGMP binding site per 130 rhodopsin molecules; the concentration of free ligand for half saturation is 2.0 +/- 0.6 microM; the apparent Hill coefficient of the bound versus free ligand relationship is 1.7 +/- 0.5; half saturation of the binding sites is sufficient for 85% activation of calcium permeability. A gating mechanism is proposed.

Animals↗
PubMed1985

Purification and characterisation of an odorant-binding protein from cow nasal tissue.

Cow nasal tissue contains a protein which shows specific binding activity for 'green' smelling compounds such as 2-isobutyl-3-methoxypyrazine. This protein has now been purified using anion-exchange fast protein liquid chromatography. The protein has a relative molecular mass of 40 0000-44 000, s = 3.1 +/- 0.3 S, pI = 4.7 +/- 0.1 with an absorbance maximum at 278 nm, and consists of two subunits with an identical relative molecular mass of 19 000. It is localised in the soluble fraction of cells from the olfactory mucosa and respiratory mucosa from the middle part of the maxillary and nasal turbinates, and is absent from all other tissues tested.

Animals↗
PubMed1981

Cyclic GMP releases calcium from disc membranes of vertebrate photoreceptors.

Physiological concentrations of cyclic guanosine 3',6'-monophosphate (cGMP) inhibit 45Ca uptake and increase 45Ca release from vertebrate photoreceptor rod outer segment disc membranes. These effects are specific for cGMP. Several facts, including the independence of these effects from added triphosphates, suggest that cGMP diminishes the Ca-binding capacity of the disc membranes. Preliminary data show that the apparent affinity constant of the cGMP-dependent Ca-binding sites of the disc membranes is of the same (or even higher) order of magnitude as that of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. As expected, the observed cGMP effects are not dependent on the light or dark conditions of the disc membranes.

Animals↗
PubMed1980

Light and GTP effects on the turbidity of frog visual membrane suspensions.

The time course of turbidity changes of frog visual membranes, dependent on osmotic shocks, on light and on nucleotide substrates or effectors of enzyme activities, were measured as absorption changes in a rapid mixing stopped-flow spectrophotometer. As a result of studies on different preparations, it is concluded that light can cause both rapid (within 50 msec) and slow (within 90 sec) changes in the turbidity of visual membranes, not associated with permeability changes, and that they are affected by GTP or its analog guanyl-5'-yl imidodiphosphate; however, the light and GTP effects are lost when a water soluble fraction containing the light-sensitive enzyme cGMP-phosphodiesterase, is removed from the rod outer segments membranes. It is suggested that the fast light and GTP-sensitive response is related to the activation of cGMP-phosphodiesterase.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1979

Phosphodiesterase and GTPase in rod outer segments. Kinetics in vitro.

The hydrolysis of cyclic guanosine monophosphate (cyclic GMP) and of guanosine triphosphate (GTP) by the broken rods of the frog retina after a flash of light have been studied in vitro with a constant perfusion method. The activation has an onset apparently instantaneous as observed with the existing possible time resolution of 3 s. The activation is followed by a partial inactivation that does not bring the activity back to the pre-flash level. GTP or the non-hydrolysable guanyl-5'-ylimidodiphosphate (GMP-PNP) is required for the normal light-activation of the phosphodiesterase and in its absence both the speed of activation and the sensitivity are greatly reduced. The activation speed, the sensitivity (threshold at approx. 0.00004% bleaching), and the kinetic constants do not exclude a direct role in the process of excitation for the phosphodiesterase and suggest a subsidiary but as yet undefined role for the GTPase.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1979

Cyclic GMP and the permeability of the disks of the frog photoreceptors.

1. The diffusion of sodium, potassium and rubidium (not chloride) ions across the disk membrane is increased by cyclic guanosine monophosphate (cyclic GMP). 2. The increase is greater for sodium than for rubidium in the 0.01-0.1 mM concentration range. 3. Cyclic adenosine monophosphate (cyclic AMP) is less efficient than cyclic GMP; GMP and guanosine triphosphate are without effect. 4. The effect is present with either 1.8 mM calcium ions or 4 mM-EGTA in the perfusion fluid. 5. The presence of the cyclic GMP phosphodiesterase on the disk membranes is not needed for this effect. 6. The effect is present in both unbleached and fully bleached membranes.

Animals↗
PubMed1978

Light-activated hydrolysis of GTP and cyclic GMP in the rod outer segments.

1. The hydrolysis of guanosine triphosphate (GTP) and the consequent formation of guanosine diphosphate (GDP) and phosphate (P1) are activated by light in a suspension of broken retinal rods: the hydrolysis rate with GTP in the micrometer concentration range is 2.5-3.5 n-mole/min per mg of rhodopsin in the preparation. 2. The ionic composition of the medium suspending the rods is not critical: the hydrolysis is present in NaCl saline solution with MG2+ as well as in Tris-HC1 buffer solution, and with the chelating agent EDTA. 3. The ionic strength is critical: the effect is reduced when the broken rods are suspended in a low salt mannitol solution, and is altogether abolished when they are separated from the mannitol solution; it reappears when the mannitol solution is added again in the presence of salts. An element essential for the effect is thus reversibly released in the mannitol solution. No hydrolytic activity on GTP, however, is found in the mannitol soluble fraction. 4. The cyclic nucleotide phosphodiesterase is eluted from the rods in the mannitol solution, and is reaggregated to the rods in the presence of salts; once recombined with the rods, it can be activated by light. 5. The activation of the phosphodiesterase by light is present in the absence of added nucleotide triphosphates.

Animals↗
PubMed1977

Metabolism of the frog outer segments: a kinetic study.

1. The reaction of the high-energy phosphate esters of the frog isolated rods, with the firefly lantern extract, has been studied by recording the luminescence in a stopped-flow apparatus. The onset of the reaction was determined by the rapid mixing of the firefly lantern extract with the high-energy phosphates released from the rods fragmented during the mixing.2. The time course of the reaction, i.e. of the luminescence, was not typical of adenosine-5'-triphosphate (ATP), indicating that the major part of the rod nucleotides is not ATP.3. The isolated rods were fragmented 1 sec-2 min after a flash of light. As soon as 1 sec after illumination, a substantial decrease of the luminescent yield has been detected in a range of light bleaching from 0.007 to 20% of the rhodopsin, indicating an early reduction of the high-energy phosphate esters.4. At longer times, flashes that bleached 7 or 20% of the rhodopsin induced a progressive decrease of the luminescent yield that was half completed in 6-9 sec, and was nearly complete in 20 sec, whereas a more or less complete recovery was observed after flashes bleaching from 0.7 to 0.007% of the rhodopsin, indicating the presence of buffering mechanisms.5. Also, the time course of the reaction was modified in a complex way after stimulation of the rods, suggesting that other nucleotides beside ATP are hydrolysed.6. The light-induced reduction of the high-energy phosphates has been observed also in broken rods, in the presence of the calcium chelating agent EGTA, suggesting that calcium is not needed for this effect.7. Cyclic guanosine monophosphate (10(-4)M) interfered with the photic effect.8. The rapid effect of light on the content of high-energy phosphate esters suggests a physiological role in the mechanism of excitation.

Adenosine Diphosphate↗
PubMed1976

On the metabolism of the rod outer segments.

1. The high energy phosphate esters available for the luminescent reaction of the firefly lantern extract correspond, in the dark adapted rods of the frog, to 7 X 10(-16) mole of ATP per rod, corresponding to ca. 1-4 mM. 2. Rods isolated from light adapted eyes contain a smaller amount. 3. The high energy phosphate esters are reduced spontaneously at a rate of 50% in 24 min, in the isolated rods in darkness. 4. Bleaching a few per cent of the rhodopsin molecules of a rod suspension induces a 60% decrease achieved in less than 12 sec. 5. The ionophore A23187 decreases the high energy phosphate esters when the extracellular free Ca concentration is greater than 10(-7) M, suggesting that ATP is consumed in pumping Ca ions out of the rods, or into the disks contained in the rods, or both.

Adenosine Triphosphate↗
PubMed1975

Effect of strong illumination on the ion efflux from the isolated discs of frog photoreceptors.

(1) Low levels of illumination do not modify the efflux of the radioisotopes 22Na, 86Rb, 36Cl, and 45Ca from the isolated discs of the photoreceptors of the frog (Rana Catesbeiana). (2) The effluxes of 22Na+, 86Rb+ and 36Cl- increase when the discs are illuminated with more than 10(4) erg/cm2 per s for a few minutes. There is no effect on the efflux of 45Ca2+ or of [14C]urea. (3) The effect is greater for monochromatic lights of wavelengths in the shorter region of the spectrum. (4) The effect is also present in bleached visual membranes.

Animals↗