Structural and Biophysical Characterization of Plasmodium falciparum Bromodomain Protein 1

Abstract

Epigenetic regulatory mechanisms are important for the growth and survival of eukaryotic organisms. Post‐translational modifications found on histone proteins in the nucleosome function as a dynamic cell signaling mechanism that controls many essential functions such as cell growth, DNA replication, and gene expression. Bromodomains are conserved protein interaction modules that specifically recognize acetylated lysine residues on histones. Among five Plasmodium species, P. falciparum is the major cause of malaria cases worldwide. According to a WHO report in 2019 there were 409,000 deaths reported worldwide and the most affected age group was of children under 5 years of age. Interestingly, the P. falciparum genome encodes eight bromodomain‐containing proteins, and bromodomain protein 1 (PfBDP1) has been shown to play an important role in malaria pathogenesis. The domain architecture of PfBDP1 includes a single C‐terminal bromodomain and several ankyrin repeats. PfBDP1 is thought to act by tethering a transcriptional activator complex to acetylated histone H3 to control genes required for parasite invasion. Additionally, PfBDP1 forms a complex with the bromodomain protein 2 (PfBDP2) to carry out its cellular functions. We hypothesized that the bromodomain is crucial for the function of PfBDP1 via recognition of acetylated lysine modifications. We carried out several histone binding assays to identify novel histone interactions of PfBDP1 bromodomain. We also utilized a combination of structural biology and biophysical approaches to identify amino acid residues critical for ligand coordination. The rise of drug‐resistance towards P. falciparum has created an urgent need to outline the molecular mechanisms driving pathogenesis in hopes of uncovering new potential drug targets. Importantly, the results from this study may improve the development of new therapeutics to treat malaria.