Structural landscape of a wide-open TPP: Insights into extreme conformational plasticity and allosteric potential.

Abstract

Trehalose-6-phosphate (T6P) homeostasis is a critical determinant of pathogen survival, positioning T6P phosphatase (TPP) as a high-priority antimicrobial target. Despite its significance, the development of universal TPP inhibitors has remained elusive. Here, we report the biochemical and structural characterization of Dermatophilus congolensis TPP (Dcon-TPP), which reveals a moderate catalytic turnover consistent with other bacterial orthologs. Our 2.9 Å crystal structure uncovers an unprecedented wide-open conformation in a state of functional disassembly, with the catalytic machinery sequestered across a ∼26 Å spatial gap. Comparative analysis reveals a remarkable ∼40 Å trajectory and 79° global rotation of the cap domain-the largest conformational rearrangement reported for the HAD superfamily to date. Our structure reveals that this extreme plasticity is linked to structural instability within the β8-strand, which likely acts as a mechanical latch to enable massive domain sweeps via a lever-arm mechanism. This inherent flexibility imposes a substantial entropic penalty on active-site pre-organization, providing a structural rationale for the modest catalytic efficiency shared by Group 3 TPPs. By elucidating this unique molecular switch, our findings suggest a cryptic allosteric site that can be targeted to lock the enzyme in an inert state, offering a promising strategy to overcome long-standing challenges in TPP inhibitor design.