A NOVEL SACCHAROMYCES-CEREVISIAE SECRETORY MUTANT POSSESSES A THERMOLABILE PHOSPHOMANNOSE ISOMERASE

A temperature-sensitive mutant of Saccharomyces cerevisiae was identified which at the restrictive temperature of 37-degrees-C is unable to secrete a number of cell wall-associated proteins and thus resembles previously reported sec mutants. In contrast to other sec mutants, however, both the temperature-sensitive growth and the secretion defects can be repaired by the addition of D-mannose to growth media. We show that the mutant possesses a single, apparently recessive mutation which leads to the production of a thermolabile phosphomannose isomerase.