National Center for
3WZ1: Catalytic Domain Of Beta-agarase From Microbulbifer Thermotolerans Jamb-a94
Crystal structure of the catalytic domain of a GH16 beta-agarase from a deep-sea bacterium, Microbulbifer thermotolerans JAMB-A94
Biosci. Biotechnol. Biochem. (2015) 79 p.625-632
A deep-sea bacterium, Microbulbifer thermotolerans JAMB-A94, has a beta-agarase (MtAgaA) belonging to the glycoside hydrolase family (GH) 16. The optimal temperature of this bacterium for growth is 43-49 degrees C, and MtAgaA is stable at 60 degrees C, which is one of the most thermostable enzymes among GH16 beta-agarases. Here, we determined the catalytic domain structure of MtAgaA. MtAgaA consists of a beta-jelly roll fold, as observed in other GH16 enzymes. The structure of MtAgaA was most similar to two beta-agarases from Zobellia galactanivorans, ZgAgaA, and ZgAgaB. Although the catalytic cleft structure of MtAgaA was similar to ZgAgaA and ZgAgaB, residues at subsite -4 of MtAgaA were not conserved between them. Also, an alpha-helix, designated as alpha4', was uniquely located near the catalytic cleft of MtAgaA. A comparison of the structures of the three enzymes suggested that multiple factors, including increased numbers of arginine and proline residues, could contribute to the thermostability of MtAgaA.