7eny

Publication Abstract from PubMed

7alpha-Hydroxysteroid dehydrogenase (7alpha-HSDH) catalyzes the dehydrogenation of a hydroxyl group at the 7alpha position in steroid substrates using NAD(+) or NADP(+) as a co-factor. Although studies have determined the binary and ternary complex structures, detailed structural changes induced by ligand and co-factor binding remain unclear, because ligand-free structures are not yet available. Here, we present the crystal structure of apo 7alpha-HSDH from Escherichia coli (Eco-7alpha-HSDH) at 2.7 A resolution. We found that the apo form undergoes substantial conformational changes in the beta4-alpha4 loop, alpha7-alpha8 helices, and C-terminus loop among the four subunits comprising the tetramer. Furthermore, a comparison of the apo structure with the binary (NAD(+))-complex and ternary (NADH and 7-oxoglycochenodeoxycholic acid)-complex Eco-7alpha-HSDH structures revealed that only the ternary-complex structure has a fully closed conformation, whereas the binary-complex and apo structures have a semi-closed or open conformation. This open-to-closed transition forces several catalytically important residues (S146, Y159, and K163) into correct positions for catalysis. To confirm the catalytic activity, we used alcohol dehydrogenase for NAD(+) regeneration to allow efficient conversion of chenodeoxycholic acid to 7-ketolithocholic acid by Eco-7alpha-HSDH. These findings demonstrate that apo Eco-7alpha-HSDH exhibits intrinsically flexible characteristics with an open conformation. This structural information provides novel insight into the 7alpha-HSDH reaction mechanism.

Crystal structure of an apo 7alpha-hydroxysteroid dehydrogenase reveals key structural changes induced by substrate and co-factor binding.,Kim KH, Lee CW, Pardhe BD, Hwang J, Do H, Lee YM, Lee JH, Oh TJ J Steroid Biochem Mol Biol. 2021 Jun 23;212:105945. doi:, 10.1016/j.jsbmb.2021.105945. PMID:34171491^[1]

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