title: Leu65 in the heme distal side is critical for the stability of the Fe(II)-O2 complex of YddV, a globin-coupled oxygen sensor diguanylate cyclase.
abstract: YddV is a globin-coupled oxygen sensor enzyme in that O(2) 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(2)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(-1)) of the Fe(II)-O(2) complex of L65G was substantially higher than that (0.011 min(-1)) of the wild-type protein. Affinities of O(2) 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(2) complex with a low autooxidation rate.
authors: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Aoba-ku, Sendai, Japan.
authors: Kyosuke
authors: K
authors: Nakajima
authors: Kenichi
authors: K
authors: Kitanishi
authors: Kazuo
authors: K
authors: Kobayashi
authors: Nagao
authors: N
authors: Kobayashi
authors: Jotaro
authors: J
authors: Igarashi
authors: Toru
authors: T
authors: Shimizu
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D005290:Ferric Compounds / Q000737:chemistry*; D006418:Heme / Q000737:chemistry; D007930:Leucine / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D019761:Phosphorus-Oxygen Lyases / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D005290:Ferric Compounds; D006418:Heme; D002248:Carbon Monoxide; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; C553251:yddV protein, E coli; D007930:Leucine; D010100:Oxygen