Deletion of a single helix from the transmembrane domain causes large changes in membrane insertion properties and secondary structure of the bacterial conjugation protein TrwB

► The TMD is needed for the correct folding of the cytosolic domain of TrwB. ► Deletion of a hydrophobic helix increases the affinity of TrwB for ATP. ► The orientation of TrwB into the membrane depends on the elements of the TMD.