Fluorescence spectrometry was used to assess the binding affinity of four flavins – riboflavin (vitamin B12), lumichrome, flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN) - with riboflavin binding protein (RBD). The precursor of FAD and FMN, co-factors for enzymes involved in energy metabolism, is riboflavin. Lumichrome, a major derivative of riboflavin, has been shown to suppress human lung cancer cell growth and has been found to be comparable to cisplatin. Riboflavin binding protein is specific for transporting riboflavin from the human mother to the fetus during pregnancy. Elevation of riboflavin binding protein (RBP) has been associated with breast cancer in women thus it might be a good biomarker to detect early breast cancer. Riboflavin binding protein (RBP) antisera has been observed to cause riboflavin depletion in the human cervical cancer cell line (HeLa). This observation suggests that RBP can be a point of intervention for therapeutic drugs against cancer. Because RBP has been implicated in cancer, researchers have been striving to develop new cancer drugs for RBP thus it is important to ascertain the binding affinity of small molecules that could be used to develop a model for drug development. Structural analysis of human folate receptor beta (HFRB), 4kmy.pdb, that is evolutionarily related to riboflavin binding protein, 6hce.pdb, has demonstrated a similarity between the two proteins thus indicating similar functions. The estimated binding energy of the four flavins with HFRB was obtained computationally and subsequent calculation of the binding affinity of the flavin-protein interactions was compared to the binding affinity of the four flavins ascertained from fluorescence spectrometry.

Comparison of the binding affinity of four flavins with riboflavin binding protein using fluorescence spectrometry and computational methods

ACS Fall 2020 Virtual Meeting

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