Phospholipase D3 (PLD3)

Hu-K4 is a human protein homologous to the K4L protein of vaccinia virus.Hu-K4 was assigned to the family of Phospholipase D proteins although so far no catalytic activity has been shown. The Hu-K4 mRNA is found in many human organs with highest expression levels in the central nervous system. As a consequence the protein is 53 amino acids larger than originally predicted, now harbouring a putative transmembrane domain. The exon/intron structure of the Hu-K4 gene reveals extensive alternative splicing in the 5' untranslated region. Due to the absence of G/C-rich regions and upstream ATG codons, the mRNA isoform in brain may be translated with higher efficacy leading to a high Hu-K4 protein concentration in this tissue. Hu-K4 is a membrane-bound protein colocalizing with protein disulfide isomerase, a marker of the endoplasmic reticulum.