Lead-binding proteins: A review

Lead-binding proteins are a series of low molecular weight proteins,analogous to metallothionein,which segregate lead in a nontoxic form in several organs (kidney,brain,lung,liver,erythrocyte). whether the lead-binding proteins in every organ are identical or different remains to be determined. in the erythrocyte,delta-aminolevulinic acid dehydratase (alad) isoforms have commanded the greatest attention as proteins and enzymes that are both inhibitable and inducible by lead. alad-2,although it binds lead to a greater degree than alad-1,appears to bind lead in a less toxic form. what may be of greater significance is that a low molecular weight lead-binding protein,approximately 10 kda,appears in the erythrocyte once blood lead exceeds 39 μg/dl and eventually surpasses the lead-binding capacity of alad. in brain and kidney of environmentally exposed humans and animals,a cytoplasmic lead-binding protein has been identified as thymosin β4,a 5kda protein. in kidney,but not brain,another lead-binding protein has been identified as acyl-coa binding protein,a 9kda protein. each of these proteins,when coincubated with liver alad and titrated with lead,diminishes the inhibition of alad by lead,verifying their ability to segregate lead in a nontoxic form. copyright © 2011 harvey c. gonick.