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An NMR-based identification of a peptide fragment from the beta-subunit of a G-protein showing specific interactions with the GBB domain of the Ste20 kinase in budding yeast.

Research paper by Surajit S Bhattacharjya, Richard R Gingras, Ping P Xu

Indexed on: 28 Jul '06Published on: 28 Jul '06Published in: Biochemical and Biophysical Research Communications



Abstract

In mitogen-activated protein kinase (MAPK) cascades of budding yeast, pheromone-induced mating signal is transmitted by interactions between the beta-subunit of a G-protein (G-beta) and the G-beta binding (GBB) domain of Ste20 kinase. Previously, mutational analyses of the beta-subunit of G-protein had identified two critical mutations which abrogate binding of the GBB domain of Ste20. In this work, we have identified, by use of NMR spectroscopy, a peptide fragment from the G-beta that shows specific interactions with the isolated GBB domain of Ste20. A model structure of the Ste20/G-beta complex reveals that the interface of the hetero-complex may be sustained by parallel orientation of two potentially interacting helical segments that are further stabilized by ionic, hydrogen bond, and helix macro-dipole interactions.