The PSEPK pathway report identifies sdhCDAB as the complete Complex II operon for TCA-cycle succinate oxidation.
"The complete four-subunit operon: cytochrome b556 (*sdhC*, K00241), membrane anchor (*sdhD*, K00242), flavoprotein (*sdhA*, K00239), and iron-sulfur subunit (*sdhB*, K00240) (Finding F005)."