Mapping the cytochrome c553 interacting site using 1H and 15N NMR

The cDNA encoding the centrosomal protein CCD41 is identical with the cDNA for the endothelial cell protein C receptor. This finding is not due to an artefact, e.g. caused by selection of false positive clones. The segment of the CCD41 cDNA encoding the protein originally termed CCD41 and deletion mutants of it were fused with the nucleotide sequence encoding the enhanced green fluorescent protein (EGFP). Transfection and expression of the full length construct produces a fusion protein mainly located in cell membranes reflecting the receptor-type protein. Deletion mutants, e.g. those where the signal sequence is deleted, result in fusion proteins which are exclusively incorporated into a small perinuclear structure which is the site of the centrosome. This result suggests that post-translational modification, namely deletion of the signal sequence, is decisive for the centrosomal location of the resulting centrosomal protein while the unprocessed protein is incorporated into cell membranes.