The role of glucose in the Kluyveromyces bulgaricus flocculation phenomenon: transduction by cAMP-dependent protein kinase pathway?
Yeast flocculation appears to be dependent on several culture conditions such as nitrogen or carbon sources. In 0.2% glucose medium Kluyveromyces bulgaricus flocculation intensity is weak (10% at maximum) by comparison with flocculation in 2% glucose medium (85% maximum). Addition of glucose to K. bulgaricus in exponential growth phase in 0.2% glucose medium produced a rapid increase of the flocculation percentage during the 30 min following the addition of glucose. cAMP and 2,4-dinitrophenol showed similar effects while cAMP-dependent protein kinase (PKA) inhibitors exhibited an antagonist effect. Moreover, the induction of flocculation did not seem to imply translation of new proteins: cycloheximide had no effect, although growth was inhibited. The induction of flocculation mainly implies ATP hydrolysis for activation or secretion of galactose-specific receptors as demonstrated by treatment with NaN(3). We propose a hypothesis that involves a PKA transduction signal leading to flocculation.
Géhin
G
G
Université Henri Poincaré, Nancy 1, UMR UHP-CNRS 7564, LCPME, Faculté de Pharmacie, Laboratoire de Biochimie Microbienne, 5 rue Albert Lebrun, P.O. Box 403, 54001 Nancy Cedex, France.
Bonaly
R
R
Coulon
J
J
D019297:2,4-Dinitrophenol / Q000494:pharmacology; D003470:Culture Media; D000242:Cyclic AMP / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D005427:Flocculation; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism*; D007716:Kluyveromyces / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D015398:Signal Transduction; D019810:Sodium Azide / Q000494:pharmacology
D003470:Culture Media; D019810:Sodium Azide; D003513:Cycloheximide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D005947:Glucose; D019297:2,4-Dinitrophenol