Leu65 in the heme distal side is critical for the stability of the Fe(II)-O<sub>2sub> complex of YddV, a globin-coupled oxygen sensor diguanylate cyclase
- 作者：Kyosuke Nakajima<sup>asup><sup> ; sup><sup>1sup> ; Kenichi Kitanishi<sup>asup><sup> ; sup><sup>1sup><sup> ; sup><sup>2sup> ; Kazuo Kobayashi<sup>bsup> ; Nagao Kobayashi<sup>csup> ; Jotaro Igarashi<sup>asup><sup> ; sup><sup>3sup> ; Toru Shimizu<sup>asup><sup> ; sup><sup>shimizu@tagen.tohoku.ac.jpsup>
- 关键词：Heme ; c-di-GMP ; Diguanylate cyclase ; Oxygen sensor
- 刊名：Journal of Inorganic Biochemistry
- 出版年：2012
- 期刊代码：53_01620134
- 类别：ch
- 出版时间：March, 2012
- 卷：108
- 期：Complete
- 页码：163-170
- 文件大小：2184 K
摘要
YddV is a globin-coupled oxygen sensor enzyme in that O<sub>2sub> binding to the Fe(II) heme in the sensor domain substantially enhances its diguanylate cyclase activity. The Fe(III) heme-bound enzyme is also the active form. Amino acid sequence comparisons indicate that Leu65 is well conserved in globin-coupled oxygen sensor enzymes. Absorption spectra of the Fe(III) heme complexes of L65G, L65M, L65Q and L65T mutants of the isolated heme domain of YddV (YddV-heme) were substantially different from that of the wild-type protein. Specifically, Soret bands of the 6-coordinated high-spin Fe(III) complexes of mutant proteins (with H<sub>2sub>O and His98 as axial ligands) were located at around 403-406 nm, distinct from that (391 nm) of the 5-coordinated high-spin Fe(III) complex of wild-type protein with His98 as the axial ligand. The autooxidation rate constant (> 0.10 min<sup>鈭?#xA0;1sup>) of the Fe(II)-O<sub>2sub> complex of L65G was substantially higher than that (0.011 min<sup>鈭?#xA0;1sup>) of the wild-type protein. Affinities of O<sub>2sub> for the Fe(II) complexes of L65G and L65T were markedly higher than that for the wild-type protein. Thus, we suggest that the well-conserved Leu65 located in the heme distal side is critical for restricting water access to the heme distal side to avoid rapid autooxidation of YddV, which needs a stable Fe(II)-O<sub>2sub> complex with a low autooxidation rate.