Testing the ability of non-methylamine osmolytes present in kidney cells to counteract the deleterious effects of urea on structure, stability and function of proteins

PLoS One. 2013 Sep 9;8(9):e72533. doi: 10.1371/journal.pone.0072533. eCollection 2013.

Abstract

Human kidney cells are under constant urea stress due to its urine concentrating mechanism. It is believed that the deleterious effect of urea is counteracted by methylamine osmolytes (glycine betaine and glycerophosphocholine) present in kidney cells. A question arises: Do the stabilizing osmolytes, non-methylamines (myo-inositol, sorbitol and taurine) present in the kidney cells also counteract the deleterious effects of urea? To answer this question, we have measured structure, thermodynamic stability (ΔG D (o)) and functional activity parameters (K m and k cat) of different model proteins in the presence of various concentrations of urea and each non-methylamine osmolyte alone and in combination. We observed that (i) for each protein myo-inositol provides perfect counteraction at 1∶2 ([myo-inositol]:[urea]) ratio, (ii) any concentration of sorbitol fails to refold urea denatured proteins if it is six times less than that of urea, and (iii) taurine regulates perfect counteraction in a protein specific manner; 1.5∶2.0, 1.2∶2.0 and 1.0∶2.0 ([taurine]:[urea]) ratios for RNase-A, lysozyme and α-lactalbumin, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Enzyme Stability
  • Humans
  • Hydrogen-Ion Concentration
  • Inositol / chemistry
  • Kidney / cytology
  • Lactalbumin / chemistry*
  • Methylamines / chemistry
  • Muramidase / chemistry*
  • Osmolar Concentration
  • Protein Denaturation
  • Protein Structure, Secondary
  • Ribonuclease, Pancreatic / chemistry*
  • Sorbitol / chemistry
  • Taurine / chemistry
  • Urea / chemistry*

Substances

  • Methylamines
  • Taurine
  • Inositol
  • Sorbitol
  • Urea
  • Lactalbumin
  • methylamine
  • Ribonuclease, Pancreatic
  • Muramidase

Grants and funding

The authors are grateful to CSIR, the Council of Scientific and Industrial Research (India), for the financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.