A REVERSIBLY PALMITOYLATED RESIDENT PROTEIN (P63) OF AN ER-GOLGI INTERMEDIATE COMPARTMENT IS RELATED TO A CIRCULATORY SHOCK RESUSCITATION PROTEIN

The recently identified 63 kDa membrane protein, p63, is a resident pr otein of a membrane network interposed in between rough ER and Golgi a pparatus. To characterize p63 at the molecular level a 2.91 kb cDNA en coding p63 has been isolated from a human placenta lambdagt10 cDNA lib rary. Sequence analysis of tryptic peptides prepared from isolated p63 confirmed the identity of the cloned gene. The translated amino acid sequence consists of 601 amino acids (65.8 kDa) with a single putative membrane-spanning region and a N-terminal cytoplasmic domain of 106 a mino acids. The human p63 cDNA exhibits a high level of sequence ident ity to the pig hepatic cDNA 3AL (accession number M27092) whose expres sion is enhanced after resuscitation from circulatory shock. An additi onal remarkable feature of p63 is that it becomes reversibly palmitoyl ated when intracellular protein transport is blocked by the drug brefe ldin A. Overexpression of p63 in COS cells led to the development of a striking tubular membrane network in the cytoplasm. This suggests tha t the protein may be determinant for the structure of the p63 compartm ent.