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Unusual Self-Hydroxylation in 4-Histidine Tetrad-Supporting Nonheme Iron Center
Nobutaka Fujieda1, Ken-Ichi Ishihama2, Haruna Ichihashi2
1Department of Applied Biological Chemistry, Graduate School of Agriculture, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka, 599-8531, Japan.
Chemistry, an Asian Journal
|April 22, 2025
Summary
The Thermotoga maritima TM1459 protein, a cupin, exhibits iron-dependent monooxygenase activity. A specific mutation facilitates self-hydroxylation of a tyrosine residue, forming an iron-catecholate complex.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- TM1459 protein from Thermotoga maritima belongs to the cupin superfamily.
- It possesses a mononuclear metal center with unknown physiological function.
- Structural data reveals octahedral coordination with histidine and water ligands.
Purpose of the Study:
- To elucidate the physiological role and enzymatic activity of the TM1459 protein.
- To investigate the mechanism of self-hydroxylation observed in a mutant form.
Main Methods:
- X-ray crystallography for structural determination.
- Spectroscopic analyses including Vis-NIR, MALDI-TOF/MS, and resonance Raman spectroscopy.
- Site-directed mutagenesis (C106V, Y7A/C106V) to probe reaction mechanisms.
Main Results:
- TM1459 protein binds Mn, Fe, and Zn ions.
- The Fe-TM1459 C106V mutant undergoes self-hydroxylation of Tyr7 to form a 3,4-dihydroxyphenylalanine residue.
- Spectroscopic data confirmed the formation of an iron-catecholate complex.
- The Y7A/C106V double mutant failed to produce the hydroxylated form, indicating Tyr7's crucial role.
Conclusions:
- Fe-TM1459 protein possesses monooxygenase activity.
- The Cys106 to Val mutation induces conformational changes enabling Tyr7 hydroxylation.
- This study reveals a novel self-hydroxylation mechanism in a cupin protein.
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