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alpha-Factor-mediatd modification of a 32P-labeled protein by MATa cells of Saccharomyces cerevisiae
Abstract:
Addition of the polypeptide mating pheromone alpha-factor to haploid MATa cells of Saccharomyces cerevisiae results in the modification of a 32P-labeled protein (P17) with an apparent Mr of 17,000 to a form having an apparent Mr of 17,500 (P17). 32P associated with both P17 and P17 exhibits an unusually rapid rate of turnover. The conversion of P17 to P17 precedes the appearance of morphologically abnormal cells and, in contrast to other responses elicited by this pheromone, this change in apparent molecular weight does not require protein synthesis. Upon removal of alpha-factor, the P17/P17 ratio returns to pretreatment levels.
Insights
The mating pheromone alpha-factor induces rapid modification of a 32P-labeled protein (P17) in yeast cells. This protein alteration occurs before cell changes and does not require new protein synthesis.
Area of Science:
- Cellular biology
- Molecular biology
- Yeast genetics
Background:
- Haploid MATa cells of Saccharomyces cerevisiae respond to mating pheromones.
- Alpha-factor is a polypeptide mating pheromone that triggers specific cellular responses.
Purpose of the Study:
- To investigate the early molecular events following alpha-factor addition in yeast.
- To characterize the modification of a specific 32P-labeled protein (P17) in response to alpha-factor.
Main Methods:
- Labeling of cellular proteins with 32P.
- Analysis of protein modification using apparent molecular weight changes.
- Monitoring protein turnover rates.
- Observing cellular morphology.
- Assessing protein synthesis requirements.
Main Results:
- Addition of alpha-factor caused a shift in 32P-labeled P17 (Mr 17,000) to P17 (Mr 17,500).
- Both P17 and P17 showed rapid 32P turnover.
- P17 to P17 conversion preceded morphological changes and did not require protein synthesis.
- The P17/P17 ratio normalized upon alpha-factor removal.
Conclusions:
- Alpha-factor induces a rapid, protein synthesis-independent modification of P17.
- This P17 modification is an early event in the yeast mating pheromone response pathway.
- The rapid turnover suggests a dynamic regulatory role for P17.