Characterization of the Rifamycin-Degrading Monooxygenase From Rifamycin Producers Implicating Its Involvement in Saliniketal Biosynthesis.

Xiao-Fu Zheng,Qiang Zhou,Shu-Ya Peng,Bin Xu,Gong-Li Tang,Xin-Qiang Liu,Hua Yuan

doi:10.3389/fmicb.2020.00971

Abstract

Rifamycin derivatives, such as rifampicin, have potent antibiotic activity and have long been used in the clinic as mainstay components for the treatment of tuberculosis, leprosy, and AIDS-associated mycobacterial infections. However, the extensive usage of these antibiotics has resulted in the rapid development of bacterial resistance. The resistance mechanisms mainly include mutations of the rifamycin target RNA polymerase of bacteria and enzymatic modifications of rifamycin antibiotics. One modification is the recently characterized rifamycin degradation catalyzed by Rox enzymes, which belong to the widely occurring flavin monooxygenases. Intriguingly, our recent sequence analysis revealed the rifamycin producers also encode Rox homologs that are not yet characterized. In this work, we expanded the study of the Rox-catalyzed rifamycin degradation. We first showed that the Rox proteins from rifamycin producers have the enzymatic rifamycin SV-degrading activity. Then we used the structurally diverse rifamycin compounds rifampicin and 16-demethylrifamycin W to probe the substrate scope and found that they each have a slightly different substrate scope. Finally, we demonstrated that Rox proteins can also catalyze the transformation of 16-demethylsalinisporamycin to 16-demethylsaliniketal A. Since 16-demethylsalinisporamycin and 16-demethylsaliniketal A are the counterpart analogs of salinisporamycin and saliniketal A, our biochemical findings not only uncover a previously uncharacterized self-resistance mechanism in the rifamycin producers, but also bridge the gap between the biosynthesis of the potential antitumor compound saliniketal A.

Highlights

Rifamycins (Rifs, Figure 1) are broad-spectrum antibiotics with potent antibiotic activity against both Gram-positive and Gram-negative bacteria (Floss and Yu, 2005)
The intensive 1D and 2D nuclear magnetic resonance (NMR) analyses of the reaction products unambiguously demonstrated that the Rox proteins from both S. venezuelae (SvRox) and N. farcinica (Nf Rox) can catalyze the linearization of the Rif antibiotics (Figure 1)
The Rox homologs are occurring in the Rif producers, such as AmRox from the Rif SV producer A. mediterranei U32, SaRox from the Rif SV producer S. arenicola, and MsRox from the 16demethylrifamycin producer Micromonospora sp

Summary

Introduction

Rifamycins (Rifs, Figure 1) are broad-spectrum antibiotics with potent antibiotic activity against both Gram-positive and Gram-negative bacteria (Floss and Yu, 2005). Their semisynthetic derivatives, such as rifampicin, have long been mainstay components for the treatment of tuberculosis, leprosy, and AIDS-associated mycobacterial infections (Floss and Yu, 2005). The four hydroxyl groups of Rif (at C1, C-8, C-21, and C-23) form critical hydrogen bonds with RpoB This strong interaction indicates that the antibiotic can effectively block the exit path for the newly-synthesized RNA (Campbell et al, 2001). The extensive usage of these antibiotics has resulted in the rapid development of bacterial resistance, and this class of antibiotics are commonly used in drug combinations (e.g., with isoniazid) and are restricted in treating tuberculosis or clinical emergencies so as to guarantee a relatively long lifespan of utility (Floss and Yu, 2005)

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