Isolation and Identification of Yeasts from Natural ... - Library Science

Mutagenesis in Yeast 37
4.13. PEPCK Mutants
28. Mutants deficient in fnrctose- 1,6-bisphosphatase, though mentioned as
belonging in this group, are not isolated by this procedure (17).
4.14. Secretory Mutants
29. The general pathway for secretion of proteins, including enzymes, is from
the site of synthesis (endoplasmic reticulum) to the Golgi body, where it is
packaged into vesicles, which are then directed to the vacuole, the mito-
chondrion, or the cytoplasmic membrane. The vesicle then fuses with the
membrane (at least in the latter case) and the protein is released into the
other compartment, for instance, the periplasmic space. The mechanism
by which the protein is transported across the cell wall and capsule, if any,
is not known; this may be by simple diffusion, although this implies the
presence of pores of a size that enzymes such as invertase or acid phos-
phatase are retained in the periplasmic space because of being too large to
pass through these channels.
30. There is an unusual mutant of this class, in which the grande form of the
yeast utilizes sucrose, but the petite mutant does not. Tests of the cell
extract shows that invertase is still present in the cell extract, but is not
transported into the periplasmic space (20).
4.15. Sulfite-Resistant Mutants
31. Interesting new examples of this class of mutant have been isolated in
S. cerevisiae, following EMS treatment, MET genes being possibly
implicated (22).
References
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mutants of Saccharomyces cerevisiae. J Bacterial. 91, 1388,1389.
2. Rickwood, D., Dujon, B., and Darley-Usmar, V. M. (1988) Yeast mitochondria,
in Yeast: A Practzcal Approach (Camphell, I. and D&us, J. H., eds.), RU, Oxford,
pp. 185-254.
3. Putrament, A., Baranowska, H., and Prazmo, W. (1973) Induction by manganese
of mitochondrial antibiotic resistance mutations rn yeast. Mol. Gen. Genet. 126,
357-366.
4. Williamson, D. H. and Fennell, D. J. (1975) The use of fluorescent DNA-binding agent
for detecting and separating yeast mitochondrial DNA, in Methods in Cell Biology,
vol. 12 (Prescott, David M., ed.), Academic, New York, pp. 335-351.
5. Von Borstel, R. C., Cain, K. T., and Steinberg, C. M. (1971) Inheritance of sponta-
neous mutability in yeast. Genetics 69, 17-27.
6. Condc, J. and Fink, G. R. (1976) A mutant of Saccharomyces cerevisiae deficient
in nuclear fusion. Proc. Natl. Acad. Sci. USA 73,365 1-3655.