A collection of haploid Saccharomyces cerevisiae deletion strains--both MAT a and alpha--was screened for mutants that exhibit low dye binding (ldb) phenotype. This phenotype has previously been associated with reduced incorporation of mannosyl phosphate groups into the mannoprotein-linked oligosaccharides. We identified 199 nonessential genes whose deletion resulted in a detectable ldb phenotype. They fell into diverse functional categories, including those involved in protein glycosylation, vacuolar function, intracellular transport, cytoskeleton organization, transcription, signal transduction, among others. The study extends the number of known genes that affect mannosyl phosphorylation of mannoprotein-linked oligosaccharides, and establishes a link with other relevant pathways in the cell, especially vacuolar function. We have assigned an LDB name to four uncharacterized ORFs identified in this study: YCL005W, LDB16; YDL146W, LDB17; YLL049W, LDB18; and YOR322C, LDB19.