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Crystal structures of the ternary complex of APH(4)-Ia/Hph with hygromycin B and an ATP analog using a thermostable mutant.

Journal of structural biology (2013-06-12)
Daisuke Iino, Yasuaki Takakura, Kazuhiro Fukano, Yasuyuki Sasaki, Takayuki Hoshino, Kanju Ohsawa, Akira Nakamura, Shunsuke Yajima
ABSTRACT

Aminoglycoside 4-phosphotransferase-Ia (APH(4)-Ia)/Hygromycin B phosphotransferase (Hph) inactivates the aminoglycoside antibiotic hygromycin B (hygB) via phosphorylation. The crystal structure of the binary complex of APH(4)-Ia with hygB was recently reported. To characterize substrate recognition by the enzyme, we determined the crystal structure of the ternary complex of non-hydrolyzable ATP analog AMP-PNP and hygB with wild-type, thermostable Hph mutant Hph5, and apo-mutant enzyme forms. The comparison between the ternary complex and apo structures revealed that Hph undergoes domain movement upon binding of AMP-PNP and hygB. This was about half amount of the case of APH(9)-Ia. We also determined the crystal structures of mutants in which the conserved, catalytically important residues Asp198 and Asn203, and the non-conserved Asn202, were converted to Ala, revealing the importance of Asn202 for catalysis. Hph5 contains five amino acid substitutions that alter its thermostability by 16°C; its structure revealed that 4/5 mutations in Hph5 are located in the hydrophobic core and appear to increase thermostability by strengthening hydrophobic interactions.

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Product Description

Sigma-Aldrich
Hygromycin B from Streptomyces hygroscopicus, suitable for plant cell culture, BioReagent, ≥60% (HPLC), lyophilized powder