. Author manuscript; available in PMC: 2021 Jul 24.

Published in final edited form as: J Mol Biol. 2020 May 28;432(16):4408–4425. doi: 10.1016/j.jmb.2020.05.020

Table 1:

Summary of couplings from EPR experiments and their meanings.

Hyperfine Coupling	Origin	Conclusion
a_iso: 55 MHz in CW	Coordinated nitrogen on equatorial histidine
a_iso: 2.50 MHz in Mims ENDOR and HYSCORE	Remote nitrogen on equatorial histidine	-
T: 2.95 MHZ in Davies ENDOR	Exchangeable proton of axial water	-
A: 1.82 MHz in HYSCORE and Mims ENDOR	Oxygen from H₂¹⁷O	Presence of axial water
Absence of weak coupling of ¹⁵N in Mims ENDOR	Axial histidine ligand	No axial histidine