Peroxisome Biogenesis Pex19p, a Farnesylated Protein Essential for

. Cells lacking Pex19pare characterized by the absence of morphologically detectable peroxisomes and mislocalization of peroxisomalmatrix proteins to the cytosol. The human HK33 gene product was identified as the putative human orthologof Pex19p. Evidence is provided that farnesylation of Pex19p takes place at the cysteine of the C-terminalCKQQ amino acid sequence. Farnesylation of Pex19p was shown to be essential for the proper function of theprotein in peroxisome biogenesis. Pex19p was shown to interact with Pex3p in vivo, and this interactionrequired farnesylation of Pex19p.