Assembly dynamics and metabolic flux redistribution mediated by accA1/accA2 functional divergence in Streptomyces...

The acyl-CoA carboxylase (YCC) complex catalyzes the first committed step in both fatty acid and polyketide biosynthesis and is therefore essential for primary and secondary metabolism in Streptomyces. In Streptomyces coelicolor, the YCC family comprises acetyl-CoA carboxylase (ACC) and propionyl-CoA carboxylase (PCC), which are homologous multi-subunit complexes sharing identical α subunits encoded by accA1 and accA2. However, the functional divergence between these two α subunit genes remains unclear. In this study, we systematically characterized accA1 and accA2 in S. coelicolor M145 through expression profiling, physiological assays, metabolomics, and Co-IP analyses. qPCR and Western blot results revealed distinct expression patterns of the two genes. Overexpression of accA2 promoted rapid biomass accumulation and enhanced primary metabolism, whereas accA1 overexpression perturbed early primary metabolism and triggered premature and elevated actinorhodin production, indicating distinct physiological functions. Metabolomic profiling further supported the notion that accA2 overexpression primarily activated primary metabolic pathways, whereas accA1 overexpression strongly induced secondary metabolism. Co-IP assays demonstrated that AccA1 and AccA2 exhibit different assembly preferences: AccA2-containing complexes remained relatively stable, whereas AccA1 displayed higher flexibility and preferentially assembled into ACC complexes. Collectively, these findings reveal that accA1 and accA2 differentially regulate carbon flux through distinct expression dynamics and assembly preferences. AccA1 predominantly channels flux toward secondary metabolite biosynthesis, while AccA2 primarily supports fatty acid and other primary metabolic processes. This work provides a theoretical basis for optimizing metabolic engineering strategies in Streptomyces.