posted on 2021-06-01, 14:05authored byChad A. Brambley, Tarah J. Yared, Marriah Gonzalez, Amanda L. Jansch, Jamie R. Wallen, Mitch H. Weiland, Justin M. Miller
Poly(aspartic
acid) (PAA) is a common water-soluble polycarboxylate
used in a broad range of applications. PAA biodegradation and environmental
assimilation were first identified in river water bacterial strains, Sphingomonas sp. KT-1 and Pedobacter sp.
KP-2. Within Sphingomonas sp. KT-1, PahZ1KT‑1 cleaves β-amide linkages to oligo(aspartic acid) and then
is degraded by PahZ2KT‑1. Recently, we reported
the first structure for PahZ1KT‑1. Here, we report
novel structures for PahZ2KT‑1 bound to either Gd3+/Sm3+ or Zn2+ cations in a dimeric
state consistent with M28 metallopeptidase family members. PahZ2KT‑1 monomers include a dimerization domain and a catalytic
domain with dual Zn2+ cations. MD methods predict the putative
substrate binding site to span across the dimerization and catalytic
domains, where NaCl promotes the transition from an open conformation
to a closed conformation that positions the substrate adjacent to
catalytic zinc ions. Structural knowledge of PahZ1KT‑1 and PahZ2KT‑1 will allow for protein engineering
endeavors to develop novel biodegradation reagents.