rpoB Mutations and Effects on Rifampin Resistance in Mycobacterium tuberculosis

Abstract

Objective: To investigate the mutations within the whole rpoB gene of Mycobacterium tuberculosis and analyze their effects on rifampin (RIF) resistance based on crystal structure.

Methods: We sequenced the entire rpoB gene in 175 tuberculosis isolates and quantified their minimum inhibitory concentrations using microplate-based assays. Additionally, the structural interactions between wild-type/mutant RpoB and RIF were also analyzed.

Results: Results revealed that a total of 34 mutations distributed across 17 different sites within the whole rpoB gene were identified. Of the 34 mutations, 25 could alter the structural interaction between RpoB and RIF and contribute to RIF resistance. Statistical analysis showed that S450L, H445D, H445Y and H445R mutations were associated with high-level RIF resistance, while D435V was associated with moderate-level RIF resistance.

Conclusion: Some mutations within the rpoB gene could affect the interaction between RpoB and RIF and thus are associated with RIF resistance. These findings could be helpful to design new antibiotics and develop novel diagnostic tools for drug resistance in TB.

Keywords: Mycobacterium tuberculosis; mutation; rifampin resistance; structure.

Figure 1

The 2D diagram showing the interactions between rifampin and wild-type RpoB (A), mutant S441L (B) or double mutant D435E & S441L (C). The rifampin (RIF) molecule is shown in the middle with a display style of ball and stick. The colored balls around RIF molecule indicate the residues involved in the direct interactions between RpoB and RIF. The green, magenta and red dash lines connecting RIF and corresponding residues indicate intermolecular hydrogen bonds, hydrophobic interactions and steric hindrance, respectively. Residues involved in van der Waals interactions are represented by light green balls without any dash line linked to RIF.

Figure 2

Interactions between rifampin and Residue 445 of wild-type/mutant RpoB. The detailed structure for rifampin (RIF) and Residue 445 of wild-type RpoB H445 (A), mutant H445R (B), mutant H445L (C), mutant H445Y (D), mutant H445C (E), mutant H445D (F), mutant H445P (G), mutant H445N (H) or mutant H445Q (I). Residue 445 of RpoB is shown in the left with a display style of Corey-Pauling-Koltun (CPK). The RIF molecule is shown in the right with a display style of stick. The intermolecular hydrogen bonds are indicated by green dashed lines.

Figure 3

Interactions between rifampin and Residue 450 of wild-type/mutant RpoB. The detailed structure for rifampin (RIF) and Residue 450 of wild-type RpoB S450 (A), mutant S450L (B), mutant S450F (C) or mutant S450G (D). Residue 450 of RpoB is shown in the left with a display style of Corey-Pauling-Koltun (CPK). The RIF molecule is shown in the right with a display style of stick. The intermolecular hydrogen bonds are indicated by green dashed lines.