Hydrogen bonding dynamics between adjacent blades in G protein subunit regulate GIRK channel activation

¹ Geisinger Medical Center
² Mount Sinai School of Medicine

^* To whom correspondence should be addressed. E-mail: dantsker{at}inka.mssm.edu.

Submitted on June 22, 2005
Revised on August 3, 2005
Accepted on 1 December 2005

	Abstract

Functionally critical domains in the subunits of the G-protein (G) do not undergo large structural rearrangements upon binding to other proteins. Here we show that a region containing Ser67 and Asp323 of G is a critical determinant of GIRK channel activation, and undergoes only small structural changes upon mutation of these residues. Using an interactive experimental and computational approach, we show that mutants that form a hydrogen bond between positions 67 and 323 do not activate a GIRK channel. We also show that in the absence of hydrogen bonding between these positions, other factors, such as the displacement of the crucial G residues Pro60 and Phe61, can impair G-mediated GIRK channel activation. our results imply that the dynamic nature of the hydrogen bonding pattern in the wild type serves an important functional role that regulates GIRK channel activation by G, and that subtle changes in the flexibility of critical domains could have substantial functional consequences. Our results further strengthen the notion that the dynamic regulation of multiple interactions between G and effectors provides for a complex regulatory process in cellular functions.

Key Words: G beta gamma, Kir3.4, computer simulations, electrophysiology, molecular dynamics, mutagenesis