Abstract
We recently reported a flavin-trafficking protein (Ftp) in the syphilis spirochete Treponema pallidum (Ftp_Tp) as the first bacterial metal-dependent FAD pyrophosphatase that hydrolyzes FAD into AMP and FMN in the periplasm. Orthologs of Ftp_Tp in other bacteria (formerly ApbE) appear to lack this hydrolytic activity; rather, they flavinylate the redox subunit, NqrC, via their metal-dependent FMN transferase activity. However, nothing has been known about the nature or mechanism of metal-dependent Ftp catalysis in either Nqr- or Rnf-redox-containing bacteria. In the current study, we identified a bimetal center in the crystal structure of Escherichia coli Ftp (Ftp_Ec) and show via mutagenesis that a single amino acid substitution converts it from an FAD-binding protein to a Mg2+-dependent FAD pyrophosphatase (Ftp_Tp-like). Furthermore, in the presence of protein substrates, both types of Ftps are capable of flavinylating periplasmic redox-carrying proteins (e.g., RnfG_Ec) via the metal-dependent covalent attachment of FMN. A high-resolution structure of the Ftp-mediated flavinylated protein of Shewanella oneidensis NqrC identified an essential lysine in phosphoester-threonyl-FMN bond formation in the posttranslationally modified flavoproteins. Together, these discoveries broaden our understanding of the physiological capabilities of the bacterial periplasm, and they also clarify a possible mechanism by which flavoproteins are generated.
Original language | English (US) |
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Pages (from-to) | 21-38 |
Number of pages | 18 |
Journal | MicrobiologyOpen |
Volume | 5 |
Issue number | 1 |
DOIs | |
State | Published - Feb 1 2016 |
Keywords
- FAD pyrophosphatase
- FMN transferase
- Flavoprotein
- Lipoprotein
- Posttranslational modification
- Redox protein
ASJC Scopus subject areas
- Microbiology