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Biomedical subjects

R Z Sabirov

Publications and source records attributed to R Z Sabirov.

31 records · Page 2Linked to original sources
PubMed1988

The structure of Staphylococcus aureus alpha-toxin-induced ionic channel.

Polyethylene glycols (PEG) with molecular weight less than or equal to 3000 were shown to effectively protect human erythrocytes from osmotic lysis induced by alpha-staphylotoxin (ST). PEG with MW less than 3000 do not change the conductivity of ion channels induced by ST in bilayer lipid membranes (BLM). Changing the bilayer from a pure phosphatidylcholine (PC) to a negatively charged phosphatidylserine (PS) film results in an asymmetry of the current-voltage characteristics. This is evidenced by the asymmetrical position of the ST-channel pore in bilayer membranes. The results obtained allow to conclude that the ST-channel is an interprotein pore filled with water (with an inner diameter of 2.5-3 nm and a length of approximately 10 nm). It is composed of six molecules of alpha-toxin from Staphylococcus aureus. The ST-channel incorporates into a membrane with only one mouth in contact with the polar lipid heads and the other one protruding 4.5-5 nm from the bilayer plane in water solution.

Bacterial Toxins↗
PubMedDate not supplied

[Ionic selectivity of melittin-modified flat lipid bilayers].

It has been established in experiments with the bilayer lipid membranes (BLM) that at pH greater than 6.6 the melittin pores are cation-selective and at lower pH they are more selective by anions. The property of melittin pores is shown to be provided by the amino group of the N-terminal glycine residue. The selectivity of melittin-containing membranes may be controlled by the transmembrane potential, the cross-section of water pores being changed. The data obtained are explained within the alimethicine-like model.

Bee Venoms↗
PubMedDate not supplied

[Selectivity of latrotoxin channel in lipid bilayers].

It is established that high initial K-TEA and Ca2(+)-K+ selectivity of channel form by latrotoxin in lipid bilayers (LT-channel) may be reduced by lowering the pH value and by increasing electrolytes concentration of solution. It is suggested that LT-channel is water-filled pore cation selectivity which is defined by the electrostatic potential on the mouth of the channel, which is induced by the ionogenic group of toxin.

Biological Transport↗
PubMedDate not supplied

[The effect of anions on the hemolytic activity of melittin].

Anions causing the melittin aggregation in the solution are shown to slow down the lytic process not preventing it completely. The equalization of the oncotic gradient through the erythrocytic membrane by the addition of polyethylene glycols of different molecular weight into the extracellular medium made it possible to establish the colloid-osmotic mechanism of hemolysis and to estimate the diameter of melittin pores. The diameter depends on the polypeptide concentration and makes up 20-30 A with its content of (6 divided by 12).10(-6) M.

Animals↗
PubMedDate not supplied

[Cation-anion selectivity of staphylococcal channels in the lipid bilayer].

It has been found that cation-anion selectivity of staphylotoxin channels in BLM of different lipid composition is determined by summary charge of ionogenic groups of protein-channel-former exhibited to the water phase. Interrelationship of staphylotoxin channel functioning is substantiated.

Animals↗
PubMedDate not supplied

[Effect of pH on the potential-dependent functioning of staphylococcal toxin channels in phosphatidylcholine bilayer].

Potential-dependence of staphylococcal toxin channels at neutral pH is poorly expressed and increases with the medium acidation. It is shown that the value of the translocating charge is practically unchanged, whereas the energy parameters of this process vary essentially. The data obtained indicate the asymmetrical disposition of ionogenic channel groups determining its behaviour in the electric field.

Bacterial Toxins↗
PubMedDate not supplied

[Conductivity and diameter of latrotoxin channels in lipid bilayers].

It is shown that approximately 9 A Ca-selective ion channels were induced in bilayer lipid membrane (BLM) from phosphatidylserine by nonpurified spider venom (Latrodectus tredicimguttatus) and by alpha-latrotoxin obtained from it. It is established that channels greatly different in conductivity have the same diameter and nearly the same charge constitution, that evidences for their claster organization. The purification process as well as freezing-thawing and long time keeping influence the channel conductivity without changing its diameter and selectivity.

Arthropod Venoms↗
PubMedDate not supplied

[Resistance of various protein channels to proteolytic degradation].

The influence of some proteolytic enzymes on the properties of the ionic channels induced in the lipid bilayer by three different toxic proteins was studied. It was found that pronase and trypsin did not decrease the conductance of the membranes modified by melittin, alpha-staphylotoxin and latrotoxin and changed its cation-anion selectivity. The dependence of melittin-channels selectivity on the medium pH was investigated. It was suggested that the carbonyl groups of peptide bond take part in defining cation selectivity of the melittin channel.

Bacterial Toxins↗
PubMedDate not supplied

[Blocking of the latrotoxin channel by cadmium ions].

Influence of cadmium ions on current-voltage characteristics of latrotoxin treated BLM was studied. It was established that the affinity of cadmium ions to cis-mouth of a channel is substantially more than to trans-mouth for all the studied voltages. It was shown than the blocking of latrotoxin channels can occur by screening of the electric potential at the entrance of the pore.

Animals↗