Structural highlights
Function
[Q8EID8_SHEON] NQR complex catalyzes the reduction of ubiquinone-1 to ubiquinol by two successive reactions, coupled with the transport of Na(+) ions from the cytoplasm to the periplasm. NqrA to NqrE are probably involved in the second step, the conversion of ubisemiquinone to ubiquinol.[HAMAP-Rule:MF_00427]
Publication Abstract from PubMed
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.
Molecular insights into the enzymatic diversity of flavin-trafficking protein (Ftp; formerly ApbE) in flavoprotein biogenesis in the bacterial periplasm.,Deka RK, Brautigam CA, Liu WZ, Tomchick DR, Norgard MV Microbiologyopen. 2015 Dec 2. doi: 10.1002/mbo3.306. PMID:26626129[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Deka RK, Brautigam CA, Liu WZ, Tomchick DR, Norgard MV. Molecular insights into the enzymatic diversity of flavin-trafficking protein (Ftp; formerly ApbE) in flavoprotein biogenesis in the bacterial periplasm. Microbiologyopen. 2015 Dec 2. doi: 10.1002/mbo3.306. PMID:26626129 doi:https://dx.doi.org/10.1002/mbo3.306
