9b1v

Publication Abstract from PubMed

The 2011 discovery of the first rare earth-dependent enzyme in methylotrophic Methylobacterium extorquens AM1 prompted intensive research toward understanding the unique chemistry at play in these systems. This enzyme, an alcohol dehydrogenase (ADH), features a La(3+) ion closely associated with redox-active coenzyme pyrroloquinoline quinone (PQQ) and is structurally homologous to the Ca(2+)-dependent ADH from the same organism. AM1 also produces a periplasmic PQQ-binding protein, PqqT, which we have now structurally characterized to 1.46-A resolution by X-ray diffraction. This crystal structure reveals a Lys residue hydrogen-bonded to PQQ at the site analogously occupied by a Lewis acidic cation in ADH. Accordingly, we prepared K(142)A- and K(142)D-PqqT variants to assess the relevance of this site toward metal binding. Isothermal titration calorimetry experiments and titrations monitored by UV-Vis absorption and emission spectroscopies support that K(142)D-PqqT binds tightly (K(d) = 0.6 +/- 0.2 muM) to La(3+) in the presence of bound PQQ and produces spectral signatures consistent with those of ADH enzymes. These spectral signatures are not observed for WT- or K(142)A-variants or upon addition of Ca(2+) to PQQ ⸦ K(142)D-PqqT. Addition of benzyl alcohol to La(3+)-bound PQQ ⸦ K(142)D-PqqT (but not Ca(2+)-bound PQQ ⸦ K(142)D-PqqT, or La(3+)-bound PQQ ⸦ WT-PqqT) produces spectroscopic changes associated with PQQ reduction, and chemical trapping experiments reveal the production of benzaldehyde, supporting ADH activity. By creating a metal binding site that mimics native ADH enzymes, we present a rare earth-dependent artificial metalloenzyme primed for future mechanistic, biocatalytic, and biosensing applications.

Structure-driven development of a biomimetic rare earth artificial metalloprotein.,Thompson PJ, Boggs DG, Wilson CA, Bruchs AT, Velidandla U, Bridwell-Rabb J, Olshansky L Proc Natl Acad Sci U S A. 2024 Aug 13;121(33):e2405836121. doi: , 10.1073/pnas.2405836121. Epub 2024 Aug 8. PMID:39116128^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.