Influence of heme environment structure on dioxygen affinity for the dual function Amphitrite ornata hemoglobin/dehaloperoxidase. Insights into the evolutional structure-function adaptations

Journal Article · Thu May 15 04:00:00 EDT 2014 · Archives of Biochemistry and Biophysics

DOI:https://doi.org/10.1016/j.abb.2014.01.010· OSTI ID:1121473

Sun, Shengfang; Sono, Masanori; Wang, Chunxue; Du, Jing; Lebioda, Lukasz; Dawson, John H. ^[1]

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1. SC

Sea worm, Amphitrite ornata, has evolved its globin (an O₂ carrier) also to serves as a dehaloperoxidase (DHP) to detoxify haloaromatic pollutants generated by competing species. A previous mutagenesis study by our groups on both DHP and sperm whale myoglobin (SW Mb) revealed some structural factors that influence the dehaloperoxidase activities (significantly lower for Mb) of both proteins. Using an isocyanide/O₂ partition constant measurement method in this study, we have examined the effects of these structural factors on the O₂ equilibrium constants (K_O2) of DHP, SW Mb, and their mutants. A clear trend of decreasing O₂ affinity and increasing catalytic activity along with the increase in the distal His N^ε–heme iron distance is observed. An H93K/T95H Mb double mutant mimicking the DHP proximal His positioning exhibited markedly enhanced O₂ affinity, confirming the essential effect of proximal His rotation on the globin function of DHP. For DHP, the L100F, T56G and M86E variants showed the effects of distal volume, distal His flexibility and proximal electronic push, respectively, on the O₂ affinity. This study provides insights into how DHP has evolved its heme environment to gain significantly enhanced peroxidase capability without compromising its primary function as an O₂ carrier.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSF
• OSTI ID: 1121473
• Journal Information: Archives of Biochemistry and Biophysics, Journal Name: Archives of Biochemistry and Biophysics Vol. 545; ISSN 0003-9861
• Country of Publication: United States
• Language: ENGLISH