ACT_SITE 307; /note="Charge relay system"; /evidence="ECO:0000250"; ACT_SITE 439; /note="Charge relay system"; /evidence="ECO:0000250"; ACT_SITE 515; /note="Charge relay system"; /evidence="ECO:0000250"; ACT_SITE 613; /note="Proton donor"; /evidence="ECO:0000255|PROSITE-ProRule:PRU10003"