Spectroscopic and Functional Determination of the Interaction of Pb2+with GATA Proteins

Publisher Website
Google Scholar
Abstract
GATA proteins are transcription factors that bind GATA DNA elements through Cys4 structural zinc-binding domains and play critical regulatory roles in neurological and urogenital development and the development of cardiac disease. To evaluate GATA proteins as potential targets for lead, spectroscopically monitored metal-binding titrations were used to measure the affinity of Pb2+ for the C-terminal zinc-binding domain from chicken GATA-1 (CF) and the double-finger domain from human GATA-1 (DF). Using this method, Pb2+ coordinating to CF and DF was directly observed through the appearance of intense bands in the near-ultraviolet region of the spectrum (250−380 nm). Absorption data collected from these experiments were best fit to a 1:1 Pb2+−CF model and a 2:1 Pb2+−DF model. Competition experiments using Zn2+ were used to determine the absolute affinities of Pb2+ for these proteins. These studies reveal that Pb2+ forms tight complexes with cysteine residues in the zinc-binding sites in GATA proteins, β1Pb = 6.4 (±2.0) × 109 M-1 for CF and β2 = 6.3 (±6.3) × 1019 M-2 for Pb2+2−DF, and within an order of magnitude of the affinity of Zn2+ for these proteins. Furthermore, Pb2+ was able to displace bound Zn2+ from CF and DF. Upon addition of Pb2+, GATA shows a decreased ability to bind to DNA and subsequently activate transcription. Therefore, the DNA binding and transcriptional activity of GATA proteins are most likely to be targeted by Pb2+ in cells and tissues that sequester Pb2+ in vivo, which include the brain and the heart.

This publication has 64 references indexed in Scilit: