Structure ofD-tagatose 3-epimerase-like protein fromMethanocaldococcus jannaschii

Abstract

PDB reference: D-tagatose 3-epimerase-like protein, 3wqoThe crystal structure of a d-tagatose 3-epimerase-like protein (MJ1311p) encoded by a hypothetical open reading frame, MJ1311, in the genome of the hyperthermophilic archaeon Methanocaldococcus jannaschii was determined at a resolution of 2.64 Å . The asymmetric unit contained two homologous subunits, and the dimer was generated by twofold symmetry. The overall fold of the subunit proved to be similar to those of the d-tagatose 3-epimerase from Pseudomonas cichorii and the d-psicose 3-epimerases from Agrobacterium tumefaciens and Clostridium cellulolyticum. However, the situation at the subunit-subunit interface differed substantially from that in d-tagatose 3-epimerase family enzymes. In MJ1311p, Glu125, Leu126 and Trp127 from one subunit were found to be located over the metal-ion-binding site of the other subunit and appeared to contribute to the active site, narrowing the substratebinding cleft. Moreover, the nine residues comprising a trinuclear zinc centre in endonuclease IV were found to be strictly conserved in MJ1311p, although a distinct groove involved in DNA binding was not present. These findings indicate that the active-site architecture of MJ1311p is quite unique and is substantially different from those of d-tagatose 3-epimerase family enzymes and endonuclease IV.

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“…Through mutation experiments deleting some C-terminal residues, it was found that the existence of a long C-terminal tail was integrant for the dramaticlly thermostability of M. loti LREase (Uechi, Sakuraba, et al, 2013). Interestingly, two D-tagatose 3-epimerase-related proteins from Thermotoga maritima and Methanocaldococcus jannaschii were already determined (Sakuraba, Yoneda, Satomura, Kawakami, & Ohshima, 2009;Uechi, Takata, Yoneda, Ohshima, & Sakuraba, 2014). The main-chain coordinates of the subunit from both of the D-tagatose 3-epimerase-like proteins were found to be similar to those of the ketose 3-epimerases.…”