A remote surface loop modulates core structure and cold activity in phosphopantetheine adenylyltransferase
Fig 5
Functional and structural effects of the SCRLS loop deletion.
(A) Schematic representation of the two-step coupled assay used to quantify PPAT catalytic activity. (B) Comparative analysis of temperature-dependent activity between wild-type MpaPPAT (green) and the MpaPPAT(Δ67–71) mutant (cyan). The wild-type enzyme sustains high catalytic activity across a broad low-temperature range (10–30 °C), whereas the loop-deletion mutant shows markedly reduced activity, especially at 10 °C and 20 °C. Activity was quantified by monitoring NADPH absorbance at 340 nm in a two-stage coupled assay. Data are presented as mean S.D. (n = 3). (C) Structural superposition illustrating the effect of the loop deletion. The wild-type MpaPPAT (green) features the distinct, solvent-exposed loop element. In the MpaPPAT(Δ67–71) mutant (cyan), this entire loop is deleted, resulting in a short, truncated turn, as expected.