Partial complementation of pyruvate dehydrogenase deficiency by independently expressed lipoyl and catalytic domains of the dihydrolipoamide acetyltransferase component.

Two compatible plasmids encoding a hybrid lipoyl domain and a defective pyruvate dehydrogenase (PDH) complex which lacks lipoyl domains, were co-expressed in a strain of Escherichia coli deleted for the PDH complex genes. In vivo complementation between the mutant complexes and the independent lipoyl domains was observed using growth tests in liquid and solid media. However, no PDH complex activity could be detected in the corresponding cell-free extracts. This suggests that untethered lipoyl domains can interact productively with the three types of active site in the multienzyme complex, but this association is disrupted in cell-free extracts.