PubMed Health⌕ Search

Biomedical subjects

K N Miasoedova

Publications and source records attributed to K N Miasoedova.

13 recordsLinked to original sources
PubMed1993

[Hexameric organization of cytochrome P-450LM4 isolated from rabbit hepatocyte endoplasmic reticulum membrane].

In pure protein preparations (monodisperse according to sedimentation analysis data) microsomal cytochrome P-450LM4 (cytochrome P-448) is represented by hexameric associates resembling those of cytochrome P-450LM2 previously characterized in this laboratory. Under conditions preventing nonspecific aggregation of membrane hemoproteins, these two cytochrome isoforms have very close sedimentation coefficients. As the LM4 displays a much higher hydrophobicity in comparison with LM2, which significantly hampers the determination of its hydrodynamic characteristics and the molecular masses of its oligomers by other trivial methods, the LM4 oligomers were characterized by comparing the dissociation patterns of LM2 and LM4 oligomers immobilized on an insoluble carrier. The dissociation regime used in those studies promoted a covalent attachment to the carrier of no more than one promoter in each oligomer.

Animals↗
PubMed1990

[Study of the structural organization of cytochrome P-450 oligomers using immobilized isoenzyme LM2].

Subunit interactions of highly purified hexameric cytochrome P-450 LM 2 has been studied using covalent binding of one of the six protomers to an insoluble matrix. Immobilized cytochrome was catalytically active in monooxygenase reactions and retained the spectral characteristics of cytochrome P-450 LM 2. High ionic strength, large scale pH changes and addition of guanidine chloride were without effect on the aggregation state of the immobilized hemoprotein. However, several detergents induced hexamer dissociation. The crucial role of hydrophobic forces in hexamer subunit interaction was demonstrated. Incubation of the immobilized cytochrome P-450 LM 2 with sonicated liposomes composed of various phospholipids did not result in oligomer dissociation and protein translocation from the matrix to the lipid phase, although the catalytic activity of the immobilized cytochrome significantly increased in the presence of liposomes. The data suggest that cytochrome P-450 LM 2 may be of hexameric structure in the native membranes.

Animals↗
PubMed1989

[Dissociation of hexamers of cytochrome P-450 LM2 in the presence of the non-ionic detergent emulgin 913].

It was shown that the maximal degree of dissociation of cytochrome P-450 LM2 hexamers in the presence of the nonionic detergent Emulgene 913 (20 degrees C) is observed at the detergent concentration of about 0.2%. Using equilibrium centrifugation in solutions of different density, the molecular mass of the dissociation product minus that of the bound detergent was found to be equal to 50 +/- 8 kDa, thus corresponding to the molecular mass of the monomer. One cytochrome P-450 LM 2 molecule binds 80 +/- 20 molecules of Emulgene 913.

Centrifugation↗
PubMed1989

[Cytochrome P-450 in proteoliposomes: oligomeric structure of the LM2 isoform].

Crosslinking of protein molecules with bifunctional reagents and subsequent electrophoresis of the modified proteins revealed the presence of cytochrome P-450 LM 2 oligomers in proteoliposome membranes obtained in different ways and differing in their phospholipid composition. Data from a comparative analysis of cytochrome P-450 oligomeric structures in solution and in membrane are suggestive of the hexameric organization of cytochrome P-450 LM 2 within proteoliposome membranes.

Animals↗
PubMed1988

[Determination of the partial specific volume of cytochrome P450 LM2].

The partial specific volume (v) of highly purified membrane protein cytochrome P450 LM2 monooxygenase from rabbit liver endoplasmatic reticulum has been estimated by various independent methods. The values of v obtained through our experiments are practically equal to the value calculated from the amino acid composition of the protein (0.75 cm3/g).

Amino Acids↗
PubMed1980

[Conformation and thermal stability of soluble and liposomal forms of cytochrome P-450].

This secondary structure of soluble cytochrome P-450 and the one incorporated into liposomes from egg lecithin and microsomal lipids has been studied. Using circular dichroism and infrared spectroscopy, it was shown that about 60% of alpha-helices are presented in the structure of haemoprotein and the rest 40% have the structure of statistical coil. The binding of haemoprotein with the type II substrates--octylamine and diaminooctan, slightly increases alpha-helices in soluble cytochrome P-450. The type I non-polar substrates--hexane and cyclohexane--do not change the conformation of isolated enzyme. Cytochrome P-450 incorporated into the artificial membranes of phosphatidyl choline and microsomal phospholipid has almost identical secondary structure as does the soluble one. Data from circular dichroism suggest that the binding of the types I and II substrates to cytochrome P-450 incorporated into lecithin liposomes and microsomal lipid liposomes does not change the conformation of the polypeptide chain. The reduction of cytochrome P-450 haem increases the degree of alpha-spiralization by 10% for soluble haemoprotein and by 5% for the membrane-bound enzyme. The thermal stability of soluble and liposomal forms of cytochrome P-450 was investigated by circular dichroism technique. The effective values of enthalpy and the temperature transition of soluble cytochrome P-450 at pH 6.9, 7,6 and 7,9 are 78, 80 and 78 kcal/mol and 47,7 degrees, 45,2 degrees and 42,4 degrees, respectively. The enzyme incorporated into the phospholipid vesicles is much more stable. The cooperative transition of soluble cytochrome is clearly expressed in contrast to the one of the membrane-bound enzyme.

Circular Dichroism↗
PubMed1979

[Accessibility of microsomal membrane proteins for protease K].

The effect of protease K on the microsomal membrane proteins was studied. It was shown that treatment of the microsomal membranes by low concentrations of protease did not remove more than 35% of total membrane proteins. Treatment by higher protease concentrations removed about 50% of the proteins. The residual protein is accessible to protease after treatment of the membranes by phospholipase A2. A simultaneous treatment of the microsomal membrane by protease and phospholipase removed up to 80% of the membrane proteins. In this way about 30% of microsomal membrane proteins are protected by the phospholipid against the action of protease K.

Animals↗
PubMed1979

[Isolation and properties of cytochrome P-450 from rabbit liver microsomes].

A purified low-spin form of cytochrome P-450 was isolated from phenobarbital-induced rabbit liver microsomes. The preparation was functionally active and free from cytochromes b5 and P-420 and phospholipids. The specific content of the cytochrome was 18 nmoles per mg of protein. At the molecular weight of the hemoprotein of 50,000, it corresponds to 90% of purification. The purified hemoprotein binds substrates of type II and some substrates of type I. The complexes formed reveal spectral properties, similar to those for the complexes of these substrates with the microsomal form of cytochrome P-450.

Animals↗