TPR-like motifs upstream and inside the PCI domain. The proposed domain topologies of selected human PCI proteins were investigated by profile techniques. Besides the common PCI domain (blue) short stretches of ~35 aa each are depicted in orange and light blue. These stretches show weak to medium similarity to TPR segments in established TPR proteins and merge seamlessly into the PCI domain in several PCI subunits. Corresponding accession numbers are listed in figure 2.