Arsenic binding proteins from human lymphoblastoid cells

Arsenic is a ubiquitous contaminant of drinking water and food. The mechani sms of the toxic action of inorganic arsenic are unknown. We report the iso lation of proteins having a high affinity for arsenic in the + 3 oxidation state that are induced by arsenite (AsIII) in human lymphoblastoid cells. T he arsenic-binding proteins were isolated using a p-aminophenylarsine oxide affinity column. At least four proteins of 50, 42, 38.5 and 19.5 kDa were isolated by elution with 10 or 100 mM 2-mercaptoethanol. Two proteins were tentatively identified as tubulin and actin on the basis of their molecular weights and previously reported affinity for the arsenic column. The ident ities of the remaining proteins are unknown. Heme oxygenase 1 was induced b y AsIII but did not bind to the arsenic affinity column. We conclude that A sIII induces multiple proteins that have variable affinities for arsenic in the + 3 state as judged by the concentration of 2-mercaptoethanol required for their elution. The arsenic binding motif of these proteins may involve three thiol groups arranged 3-6 Angstrom apart by the tertiary structure o f the protein as suggested by others. These proteins may serve as high affi nity binding sites for AsIII and may be involved in the biological action o f AsIII. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights res erved.