Diphthamide synthesis is linked to the eEF2-client chaperone machinery

The diphthamide modification of eukaryotic translation elongation factor (eEF2) is important for accurate protein synthesis. While the enzymes for diphthamide synthesis are known, coordination of eEF2 synthesis with the diphthamide modification to maintain only modified eEF2 is unknown. Physical and genetic interactions extracted from BioGRID show a connection between diphthamide synthesis enzymes and chaperones in yeast. This includes the Hsp90 co-chaperones Hgh1 and Cpr7. The respective co-chaperone deletion strains contained eEF2 without diphthamide. Notably, strains deficient in other co-chaperones showed no defect in the eEF2-diphthamide modification. Our results demonstrate that diphthamide synthesis involves not only Dph enzymes but also the eEF2-interacting co-chaperones Hgh1 and Cpr7 and may thus require a conformational state of eEF2 which is maintained by specific (co-)chaperones.