Publication
Native mass spectrometry identifies an alternative DNA-binding pathway for BirA from Staphylococcus aureus
Publisher:
Springer Science and Business Media LLC
Date:
26-02-2019
DOI:
10.1038/S41598-019-39398-6
Abstract: An adequate supply of biotin is vital for the survival and pathogenesis of Staphylococcus aureus . The key protein responsible for maintaining biotin homeostasis in bacteria is the biotin retention protein A (BirA, also known as biotin protein ligase). BirA is a bi-functional protein that serves both as a ligase to catalyse the biotinylation of important metabolic enzymes, as well as a transcriptional repressor that regulates biotin biosynthesis, biotin transport and fatty acid elongation. The mechanism of BirA regulated transcription has been extensively characterized in Escherichia coli , but less so in other bacteria. Biotin-induced homodimerization of E. coli BirA ( Ec BirA) is a necessary prerequisite for stable DNA binding and transcriptional repression. Here, we employ a combination of native mass spectrometry, in vivo gene expression assays, site-directed mutagenesis and electrophoretic mobility shift assays to elucidate the DNA binding pathway for S. aureus BirA ( Sa BirA). We identify a mechanism that differs from that of Ec BirA, wherein Sa BirA is competent to bind DNA as a monomer both in the presence and absence of biotin and/or MgATP, allowing homodimerization on the DNA. Bioinformatic analysis demonstrated the Sa BirA sequence used here is highly conserved amongst other S. aureus strains, implying this DNA-binding mechanism is widely employed.