Rescue of the neuroblastoma mutant of the human nucleoside diphosphate kinase A/nm23-H1 by the natural osmolyte trimethylamine-N-oxide

Abstract

The point mutation S120G in human nucleoside diphosphate kinase A, identified in patients with neuroblastoma, causes a protein folding defect. The urea‐unfolded protein cannot refold in vitro, and accumulates as a molten globule folding intermediate. We show here that the trimethylamine‐N‐oxide (TMAO) corrects the folding defect and stimulated subunit association. TMAO also substantially increased the stability to denaturation by urea of both wild‐type and S120G mutant. A non‐native folding intermediate accumulated in the presence of 4.5–7 M urea and of 2 M TMAO. It was inactive, monomeric, contained some secondary structure but no tertiary structure and displayed a remarkable stability to denaturation.