cytochrome-c-t and maleic-acid

Cytochrome

Topics: Cryoelectron Microscopy; Cytochromes b; Cytochromes c; Electron Transport Complex III; Lipids; Oxidation-Reduction; Quinones; Rhodobacter sphaeroides; Styrene

Interest has recently been shown again in colistin because of the increased prevalence of infections caused by multidrug-resistant Gram-negative bacteria. Although the potential for nephrotoxicity is a major dose-limiting factor in colistin use, little is known about the mechanisms that underlie colistin-induced nephrotoxicity. In this study, we focused on an endocytosis receptor, megalin, that is expressed in renal proximal tubules, with the aim of clarifying the role of megalin in the kidney accumulation and nephrotoxicity of colistin. We examined the binding of colistin to megalin by using a vesicle assay. The kidney accumulation, urinary excretion, and concentrations in plasma of colistin in megalin-shedding rats were also evaluated. Furthermore, we examined the effect of megalin ligands and a microtubule-depolymerizing agent on colistin-induced nephrotoxicity. We found that cytochrome c, a typical megalin ligand, inhibited the binding of colistin to megalin competitively. In megalin-shedding rats, renal proximal tubule colistin accumulation was decreased (13.5 ± 1.6 and 21.3 ± 2.6 μg in megalin-shedding and control rats, respectively). Coadministration of colistin and cytochrome c or albumin fragments resulted in a significant decrease in urinary N-acetyl-β-d-glucosaminidase (NAG) excretion, a marker of renal tubular damage (717.1 ± 183.9 mU/day for colistin alone, 500.8 ± 102.4 mU/day for cytochrome c with colistin, and 406.7 ± 156.7 mU/day for albumin fragments with colistin). Moreover, coadministration of colistin and colchicine, a microtubule-depolymerizing agent, resulted in a significant decrease in urinary NAG excretion. In conclusion, our results indicate that colistin acts as a megalin ligand and that megalin plays a key role in the accumulation in the kidney and nephrotoxicity of colistin. Megalin ligands may be new targets for the prevention of colistin-induced nephrotoxicity.

Topics: Acetylglucosaminidase; Animals; Anti-Bacterial Agents; Blotting, Western; Colchicine; Colistin; Cytochromes c; Kidney; Low Density Lipoprotein Receptor-Related Protein-2; Male; Maleates; Rats; Rats, Wistar

The interaction of cytochrome c (cyt c) with poly(isobutylene-alt-maleic acid) (PIMA) and poly(1-tetradecene-alt-maleic acid) (PTMA) was studied using circular dichroism, absorption spectroscopy, and atomic force microscopy to investigate the electrostatic and hydrophobic influence of the copolymers on the structure of cyt c. At pH 7.4, the interaction of PIMA with cyt c can only partly disturb the integrity of the heme pocket, while PTMA has very intensive influence on the structure of cyt c. After adding 0.15 M NaCl, PIMA-cyt c complexes dissociate, and the released cyt c recovers its native structure, whereas NaCl has no significant influence on PTMA-cyt c complexes. GuHCl (0.5 M) destroys PTMA-cyt c complexes, forming GuHCl-PTMA precipitates; the cyt c released from the complexes regenerates its native structure. In comparison with electrostatic interaction, hydrophobic interaction leads to more stable polymer-cyt c complexes and more intensive influence on cyt c structure, but cyt c can recover its native state after release.

Topics: Alkenes; Animals; Cytochromes c; Guanidine; Heart; Horses; Hydrogen-Ion Concentration; Maleates; Microscopy, Atomic Force; Osmolar Concentration; Polymers; Protein Conformation; Protein Structure, Secondary; Sensitivity and Specificity; Sodium Chloride; Static Electricity; Structure-Activity Relationship; Temperature

Apo cytochrome c (apo cyt c) tends to aggregate at alkali pH. Poly(isobutylene-alt-maleic acid) (PIMA) is soluble molecularly, whereas poly(1-tetradecene-alt-maleic acid) (PTMA) forms particles that tend to dissociate by increasing pH and decreasing concentration. Dynamic light scattering and surface plasmon resonance are used to investigate the interactions of PIMA and PTMA with apo cyt c at different pH values to understand the mechanism of the interactions. When the positive or negative charges are in excess, the copolymer-protein complex particles can be stabilized by the charges on the surface. When the ratio of the positive to negative charges is close to the stoichiometric value, precipitation occurs. At pH 11.8, both PTMA and apo cyt c carry negative charges, but the hydrophobic interaction makes them form complexes. A competition exists between the interaction of the copolymer with apo cyt c and the self-aggregation of PTMA or apo cyt c alone. The interaction of PIMA or PTMA with apo cyt c at neutral and alkali pH destroys the aggregation of PTMA or apo cyt c and forms new complex particles.

Topics: Alkenes; Cytochromes c; Light; Maleates; Microscopy, Atomic Force; Polymers; Scattering, Radiation; Surface Plasmon Resonance