Structural characterization and functional analysis of juvenile hormone diol kinase from the silkworm, Bombyx mori

Abstract

Juvenile hormone diol kinase (JHDK) is an important enzyme involved in the juvenile hormone metabolism pathway, which catalyzes the phosphorylation of juvenile hormone diol to form the polar metabolite JH diol phosphate. Here, we reported the first crystal structure of insect JHDK from Bombyx mori, BmJHDK-L2, determined at a resolution of 1.22 Å. The structure of BmJHDK-L2 mainly comprises of eight α-helical segments linked with loops, forming four helix-loop-helix motifs. In these four helix-loop-helix motifs with only one calcium ion bound in the first motif. Circular dichroism spectra indicated that BmJHDK-L2 has strong thermal stability, which is independent of the divalent cation. The structure of BmJHDK-L2 further allowed us to define an ATP-binding site using computational simulation and binding assays, providing a structural basis for development of inhibitor of JHDK. Moreover, the expression profile of BmJHDK-L2 indicated a predominant role in juvenile hormone metabolism in the Malpighian tubules of silkworm. Collectively, these findings expand our knowledge regarding the structural and biochemical features of insect JHDK proteins.