THE N-TERMINAL REGION OF THE ALPHA-SUBUNIT OF THE TRAP COMPLEX HAS A CONSERVED CLUSTER OF NEGATIVE CHARGES

The alpha-subunit of the TRAP complex (TRAP alpha) is a single-spannin g membrane protein of the endoplasmic reticulum (ER) which is found in proximity of nascent polypeptide chains translocating across the memb rane. Here, we demonstrate the widespread occurrence of TRAP alpha in eukaryotes as indicated by its existence in man, fish and plants. Desp ite the fact that the sequence homology is much lower than for other p roteins in the translocation site, the overall topology, the location of the glycosylation sites and, most interestingly, the distribution o f charges are conserved. These data indicate that the TRAP complex has a ubiquitous function.