Evolutionary divergence of chloroplast FAD synthetase proteins

Abstract

BackgroundFlavin adenine dinucleotide synthetases (FADSs) - a group of bifunctional enzymes that carry out the dual functions of riboflavin phosphorylation to produce flavin mononucleotide (FMN) and its subsequent adenylation to generate FAD in most prokaryotes - were studied in plants in terms of sequence, structure and evolutionary history.ResultsUsing a variety of bioinformatics methods we have found that FADS enzymes localized to the chloroplasts, which we term as plant-like FADS proteins, are distributed across a variety of green plant lineages and constitute a divergent protein family clearly of cyanobacterial origin. The C-terminal module of these enzymes does not contain the typical riboflavin kinase active site sequence, while the N-terminal module is broadly conserved. These results agree with a previous work reported by Sandoval et al. in 2008. Furthermore, our observations and preliminary experimental results indicate that the C-terminus of plant-like FADS proteins may contain a catalytic activity, but different to that of their prokaryotic counterparts. In fact, homology models predict that plant-specific conserved residues constitute a distinct active site in the C-terminus.ConclusionsA structure-based sequence alignment and an in-depth evolutionary survey of FADS proteins, thought to be crucial in plant metabolism, are reported, which will be essential for the correct annotation of plant genomes and further structural and functional studies. This work is a contribution to our understanding of the evolutionary history of plant-like FADS enzymes, which constitute a new family of FADS proteins whose C-terminal module might be involved in a distinct catalytic activity.

Uptake and Metabolism of Antibiotics Roseoflavin and 8-Demethyl-8-Aminoriboflavin in Riboflavin-Auxotrophic Listeria monocytogenes

“…FAD is the predominant flavin-derived cofactor in all cells (11), and we speculate that the physiological role of Lmo0728 (RibC) is to support Lmo1329 (RibCF) with regard to the synthesis of FAD. To our knowledge, this is the first experimental proof of a monofunctional FAD synthetase in bacteria, although the presence of such an enzyme has been proposed (37). The only other known bacterial monofunctional flavin-metabolizing enzyme is the regulator RibR from B. subtilis, which, in addition to being a regulator, is a flavokinase.…”

Production of riboflavin and related cofactors by biotechnological processes

“…In most prokaryotes, the synthesis of FMN and FAD is executed by a bifunctional RFK/FMNAT enzyme, which is usually known as FAD synthetase (FADS). The C-terminal domain catalyzes FMN synthesis from RF (RFK activity), and the N-terminal domain transforms FMN into FAD (FMNAT) [55][56][57][58][59][60][61]. In addition to bifunctional FADS, bacteria such as B. subtilis [62] and Streptococcus agalactiae (S. agalactiae) [63] possess monofunctional enzymes with only RFK activity.…”

Structural insights into the synthesis of FMN in prokaryotic organisms

“…The enzymes catalysing these activities are very diverse, with different protein folds encoding the same activities, as well as monofunctional and bifunctional members. In general mammals and yeast have two independent monofunctional enzymes that catalyse each of the reactions, while bacteria contain a single bifunctional polypeptide called FAD synthetase (FADS) (Serrano, Ferreira et al, 2013;Frago et al, 2008;Yruela et al, 2010;Krupa et al, 2003). Whereas the N-terminal module of FADS lacks structural homology to eukaryotic FMNATs, the kinase module is homologous to monofunctional RFKs (Herguedas et al, 2010;Huerta et al, 2009).…”