Las21 (Yjl062W) is a member of the major facilitator super family, possessing multimembrane spanning domains. The LAS21 gene was identified as a responsible gene for a Saccharomyces cerevisiae mutan which shows sensitivity to a local anestheticum, tetracaine. The null las21 mutant (las21Δ) is viable but shows temperature sensitive growth. We found, in addition to this phenotype, that the las21Δ strain shows a number of defects; mating deficiency, calcofluor resistance, and formation of Zymolyase sensitive spores. Temperature sensitive growth of the las21Δ mutant was found to be suppressed by 0.1 M MgSO₄. Two multicopy suppressors were obtained. They are ECM33 (YBR078W) and PIR2/HSP150 (YJR159W) both have some roles in an extracellular function. The common features of the suppressors, genetic and physiological, of the las21 Δ mutation suggest that Las21 participates in a global activity of extracellular phenomena. The las 21 phenotypes are consistent with the idea that Las21/Gpi7 acts in metabolism of glycosylphosphatidylinositol.