Enhanced PrrAB system activation and restricted farnesyl pyrophosphate diversion underlie high coenzyme Q10 accumulation in Rhodobacter sphaeroides HY01

Abstract

The industrial Rhodobacter sphaeroides HY01 accumulates an exceptionally high level of coenzyme Q₁₀ (Q₁₀), but the underlying mechanisms remain incompletely understood. Given the central role of Q₁₀ in respiratory electron transport, previous observation of reduced expression of cbb₃-type cytochrome c oxidase genes in HY01 suggested a potential mechanistic link. In this study, we found that cbb₃ oxidase activity in HY01 was only 21.8–32.8 % of that in the wild-type 2.4.1, and restoring this activity led to a 64.4 % decrease in Q₁₀ accumulation, demonstrating a strong inverse correlation. This correlation was found to be mediated by the activation of the PrrAB two-component regulatory system, which is negatively regulated by cbb₃ oxidase. However, disruption of cbb₃ oxidase in 2.4.1 alone was insufficient to reproduce the high Q₁₀ accumulation phenotype, indicating that additional factors may be required. Previous research also revealed restricted synthesis of geranylgeranyl diphosphate (GGPP) in HY01, which likely reduces the diversion of the Q₁₀ precursor farnesyl diphosphate (FPP). Reconstituting this metabolic constraint in wild-type strain, combined with fine-tuning of PrrAB system activation, resulted in up to a 218.0 % increase in Q₁₀ accumulation, achieving a level nearly identical to HY01. Combining mechanistic investigation and inverse metabolic engineering, this study demonstrates that the high Q₁₀ accumulation in HY01 results from the synergistic effects of enhanced PrrAB activation and restricted FPP diversion, providing new insights into the key factors underlying high-level Q₁₀ accumulation in R. sphaeroides.