Dynamic acetylation of a conserved lysine impacts glycerol kinase activity and abundance in the haloarchaeon Haloferax volcanii

TL;DR

This study shows that lysine acetylation regulates glycerol kinase activity and stability in Haloferax volcanii, a type of archaea, helping it adapt to different carbon sources.

Contribution

The study identifies lysine acetylation as a novel regulatory mechanism for glycerol kinase in archaea, specifically in Haloferax volcanii.

Findings

Lysine acetylation at residue K153 enhances HvGK activity, stability, and abundance during glycerol metabolism.

The acetylation mimic K153Q supports glycerol growth, while the nonacetylatable K153R variant does not.

Pat2 acetyltransferase is responsible for HvGK acetylation, and its absence reduces HvGK levels.

Abstract

Lysine acetylation is a key regulator of metabolism, but its role in archaeal carbon metabolism remains unclear. In halophilic archaea such as Haloferax volcanii, glycerol kinase (GK, glpK) catalyzes the phosphorylation of glycerol to glycerol-3-phosphate, the first committed step in glycerol catabolism. Unlike bacterial GKs, which are typically repressed during glucose metabolism, H. volcanii prefers glycerol as a carbon and energy source rather than glucose, suggesting that GK across species is regulated by distinct mechanisms. Here, we show that lysine acetylation enhances H. volcanii GK (HvGK) activity, allosteric behavior, stability, and cellular abundance during growth on glycerol. Lysine residue 153 (K153), located within a conserved flexible loop, was identified as the primary acetylation site and reached up to 78% acetylation occupancy in glycerol-grown cells, as determined by AQUA-MS. Shifting from glucose to glycerol increased both HvGK activity and K153 acetylation. Functional assays revealed that HvGK and the acetylation mimic variant K153Q supported growth on glycerol, while the nonacetylatable variant K153R did not. The K153R substitution also reduced protein stability, as shown by thermal shift assays, and altered cooperative substrate binding behavior. The GNAT-family acetyltransferase Pat2 was found responsible for acetylating HvGK at K153. In Δpat2 mutants, HvGK levels were significantly reduced but rescued by the K153Q variant, indicating acetylation protects HvGK from degradation. Together, these findings reveal that lysine acetylation dynamically coordinates HvGK structure and function in response to carbon source availability, positioning acetylation as a key posttranslational mechanism of metabolic control in H. volcanii.

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