9xwd | pdb_00009xwd
Phosphopantetheine adenylyltransferase (PPAT) from psychrophilic methanotroph Methylocapsa palsarum
Structural highlights
FunctionA0A1I4C747_9HYPH Reversibly transfers an adenylyl group from ATP to 4'-phosphopantetheine, yielding dephospho-CoA (dPCoA) and pyrophosphate.[HAMAP-Rule:MF_00151] Publication Abstract from PubMedPhosphopantetheine adenylyltransferase (PPAT), a key enzyme in the universal Coenzyme A biosynthetic pathway, is essential for cellular metabolism. However, the adaptive mechanisms of PPAT in psychrophilic (cold-adapted) organisms remain poorly understood. Here, we characterize PPAT from the psychrophilic methanotroph Methylocapsa palsarum (MpaPPAT). Sequence analysis identified a unique five-amino-acid insertion (SCRLS) within a surface-exposed loop, a feature conserved among psychrophilic homologues. To investigate its function, we determined the crystal structures of wild-type (WT) MpaPPAT and a loop-deletion mutant (MpaPPAT(Delta67-71)) and performed comparative biochemical analyses. Structurally, MpaPPAT forms a dimer-of-trimers hexamer. Biochemically, WT MpaPPAT maintains high catalytic activity at low temperatures (10-20 degrees C), whereas the MpaPPAT(Delta67-71) mutant exhibits impaired cold activity. The mutant structure reveals that the deletion of the distant surface loop induces a long-range allosteric change, resulting in a dual impairment: 1) a stabilization and rigidification ("clamping") of the central alpha-helix 4 (H4) at the hexameric core interface, and 2) a dramatic shift in the central pore's electrostatic potential from positive (WT) to negative (mutant). Our findings reveal that the SCRLS insertion is a critical allosteric modulator that provides a sophisticated dual mechanism for enzymatic cold adaptation. It maintains the conformational flexibility of the hexameric core, preventing the "clamping" effect, and simultaneously ensures a positively charged central channel to electrostatically steer negatively charged substrates (ATP and phosphopantetheine) into the active site, thereby overcoming the kinetic challenges of a low-temperature environment. A remote surface loop modulates core structure and cold activity in phosphopantetheine adenylyltransferase.,Nam Y, Hwang J, Kim B, Lee JH, Do H PLoS One. 2026 Mar 12;21(3):e0342296. doi: 10.1371/journal.pone.0342296. , eCollection 2026. PMID:41818184[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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