62746-55-8Relevant academic research and scientific papers
Structural and kinetic studies on RosA, the enzyme catalysing the methylation of 8-demethyl-8-amino- d -riboflavin to the antibiotic roseoflavin
Tongsook, Chanakan,Uhl, Michael K.,Jankowitsch, Frank,Mack, Matthias,Gruber, Karl,Macheroux, Peter
, p. 1531 - 1549 (2016/04/26)
N,N-8-demethyl-8-amino-d-riboflavin dimethyltransferase (RosA) catalyses the final dimethylation of 8-demethyl-8-amino-d-riboflavin (AF) to the antibiotic roseoflavin (RoF) in Streptomyces davawensis. In the present study, we solved the X-ray structure of RosA, and determined the binding properties of substrates and products. Moreover, we used steady-state and rapid reaction kinetic studies to obtain detailed information on the reaction mechanism. The structure of RosA was found to be similar to that of previously described S-adenosylmethionine (SAM)-dependent methyltransferases, featuring two domains: a mainly α-helical 'orthogonal bundle' and a Rossmann-like domain (α/β twisted open sheet). Bioinformatics studies and molecular modelling enabled us to predict the potential SAM and AF binding sites in RosA, suggesting that both substrates, AF and SAM, bind independently to their respective binding pocket. This finding was confirmed by kinetic experiments that demonstrated a random-order 'bi-bi' reaction mechanism. Furthermore, we determined the dissociation constants for substrates and products by either isothermal titration calorimetry or UV/Vis absorption spectroscopy, revealing that both products, RoF and S-adenosylhomocysteine (SAH), bind more tightly to RosA compared with the substrates, AF and SAM. This suggests that RosA may contribute to roseoflavin resistance in S. davawensis. The tighter binding of products is also reflected by the results of inhibition experiments, in which RoF and SAH behave as competitive inhibitors for AF and SAM, respectively. We also showed that formation of a ternary complex of RosA, RoF and SAH (or SAM) leads to drastic spectral changes that are indicative of a hydrophobic environment. Database Structural data are available in the Protein Data Bank under accession number 4D7K. 8-demethyl-N,N-8-amino-D-riboflavin dimethyltransferase (RosA) catalyzes the dimethylation of 8-demethyl-8-amino-D-riboflavin (AF) to the antibiotic roseoflavin (RoF) in Streptomyces davawensis via a random-order mechanism. RosA has a structural topology similar to other S-adenosylmethionine (SAM)-dependent methyltransferases. Slow synthesis of RoF and the tight binding of the products, RoF and SAH, suggest that RosA may contribute to a mechanism for RoF resistance.
Photo-degradation behaviour of roseoflavin in some aqueous solutions
Tyagi,Penzkofer,Mathes,Hegemann
experimental part, p. 27 - 36 (2010/06/19)
An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.
