Molecular Basis of Mannose Recognition by Pradimicins and their Application to Microbial Cell Surface Imaging.

Naturally occurring pradimicins (PRMs) show specific recognition of d -mannose (d -Man) in aqueous media, which has never been achieved by artificial small molecules. Although the Ca2+-mediated dimerization of PRMs is essential for their d -Man binding, the dimeric structure has yet to be elucidated, leaving the question open as to how PRMs recognize d -Man. Thus, we herein report the structural elucidation of the dimer by a combination of X-ray crystallography and solid-state NMR spectroscopy. Coupled with our previous knowledge regarding the d -Man binding geometry of PRMs, elucidation of the dimer allowed reliable estimation of the mode of d -Man binding. Based on the binding model, we further developed an azide-functionalized PRM derivative (PRM-Azide) with d -Man binding specificity. Notably, PRM-Azide stained Candida rugosa cells having mannans on their cell surface through conjugation with the tetramethylrhodamine fluorophore. The present study provides the practical demonstration that PRMs can serve as lectin mimics for use in glycobiological studies. • Dimeric structure of pradimicin (PRM) with mannose binding ability is elucidated • NMR-based calculations provide a reliable binding model of PRM with mannose • Azide-functionalized PRM (PRM-Azide) shows mannose binding specificity in water • PRM-azide fluorescently stains cell wall mannans of Candida rugosa Nakagawa et al. report the structural elucidation of pradimicin (PRM) dimer, and provide a possible answer as to how PRM recognizes mannose (Man). They also disclose that an azide-functionalized PRM retains mannose binding specificity in water, and fluorescently stains cell wall mannans of Candida rugosa. [ABSTRACT FROM AUTHOR]