6ogm

Publication Abstract from PubMed

A 4-oxalocrotonate tautomerase (4-OT) trimer has been isolated from Burkholderia lata, and a kinetic, mechanistic, and structural analysis has been performed. The enzyme is the third described oligomer state for 4-OT along with a homo- and heterohexamer. The 4-OT trimer is part of a small subset of sequences (133 sequences) within the 4-OT subgroup of the tautomerase superfamily (TSF). The TSF has two distinct features: members are composed of a single beta-alpha-beta unit (homo- and heterohexamer) or two consecutively joined beta-alpha-beta units (trimer) and generally have a catalytic amino-terminal proline. The enzyme, designated as fused 4-OT, functions as a 4-OT where the active site groups (Pro-1, Arg-39, Arg-76, Phe-115, Arg-127) mirror those in the canonical 4-OT from Pseudomonas putida mt-2. Inactivation by 2-oxo-3-pentynoate suggests that Pro-1 of fused 4-OT has a low p Ka enabling the prolyl nitrogen to function as a general base. A remarkable feature of the fused 4-OT is the absence of P3 rotational symmetry in the structure (1.5 A resolution). The asymmetric arrangement of the trimer is not due to the fusion of the two beta-alpha-beta building blocks because an engineered "unfused" variant that breaks the covalent bond between the two units (to generate a heterohexamer) assumes the same asymmetric oligomerization state. It remains unknown how the different active site configurations contribute to the observed overall activities and whether the asymmetry has a biological purpose or role in the evolution of TSF members.

Structural, Kinetic, and Mechanistic Analysis of an Asymmetric 4-Oxalocrotonate Tautomerase Trimer.,Baas BJ, Medellin BP, LeVieux JA, de Ruijter M, Zhang YJ, Brown SD, Akiva E, Babbitt PC, Whitman CP Biochemistry. 2019 Jun 4;58(22):2617-2627. doi: 10.1021/acs.biochem.9b00303. Epub, 2019 May 23. PMID:31074977^[1]

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