The adaptive filter of the yeast galactose pathway

JOURNAL OF THEORETICAL BIOLOGY

卷:242

Article

Smidtas, Serge ; Schachter, Vincent ; Kepes, Francois

关键词: galactose switch;    yeast;    adaptive filter;    feedback loop;    qualitative modeling;    interaction networks;   

DOI  :  10.1016/j.jtbi.2006.03.005

来源: Elsevier

【 摘 要 】

In the yeast Saccharomyces cerevisiae, the interplay between galactose, Ga13p, Ga180p and Ga14p determines the transcriptional status of the genes required for galactose utilization. After an increase in galactose concentration, galactose molecules bind onto Ga13p. This event leads via Ga180p to the activation of Ga14p, which then induces GAL3 and GAL80 gene transcription. Here we propose a qualitative dynamical model, whereby these molecular interaction events represent the first two stages of a functional feedback loop that closes with the capture of activated Ga14p by newly synthesized Ga13p and Ga180p, decreasing transcriptional activation and creating again the protein complex that can bind incoming galactose molecules. Based on the differential time-scales of faster protein interactions versus slower biosynthetic steps, this feedback loop functions as a derivative filter where galactose is the input step signal, and released Ga14p is the output derivative signal. One advantage of such a derivative filter is that GAL genes are expressed in proportion to cellular requirements. Furthermore, this filter adaptively protects the cellular receptors from saturation by galactose, allowing cells to remain sensitive to variations in galactose concentrations rather than to absolute concentrations. Finally, this feedback loop, by allowing phosphorylation of some active Ga14p, may be essential to initiate the subsequent long-term response. (c) 2006 Elsevier Ltd. All rights reserved.

【 授权许可】

Free