YEB3/VAC8 encodes a myristylated armadillo protein of the Saccharomyces cerevisiae vacuolar membrane that functions in vacuole fusion and inheritance.

Armadillo (Arm) repeat proteins such as beta-catenin and alpha-karyopherin (importin) are thought to mediate the docking of cargo at membrane-associated cytoskeletal elements. YEB3 encodes an uncharacterized Saccharomyces cerevisiae protein that contains eleven tandem Arm repeats. While YEB3 is nonessential for growth, yeb3delta cells accumulated numerous small vacuoles and are defective in vacuolar inheritance. A functional Yeb3p-green fluorescent protein (GFP) chimera localized to vacuolar membranes. Confocal microscopy revealed that Yeb3p-GFP is localized over the surface of the vacuole, but is concentrated approximately 5- to 7-fold in bands located between clustered vacuoles. N-terminal myristylation of Yeb3p is required for vacuolar localization. The first 69 amino acids of Yeb3p were sufficient to target a GFP reporter protein to the vacuolar membrane; however, this fusion protein also localized to the plasma membrane, indicating that additional sequence is required for exclusive steady state vacuolar localization. By analogy to the function of beta-catenin in cell-cell adhesion, alpha-karyopherin in nuclear transport, and smgGDS in the control of ras-like GTPases, Yeb3p may provide a link between vacuoles and the actin cytoskeleton during vacuolar inheritance and fusion and perhaps mediate the assembly of a GTPase regulated docking complex.