Understanding the molecular basis of interaction specificity between RGS (regulator of G protein signaling) proteins and heterotrimeric () G proteins would enable the manipulation of RGS-G protein interactions, explore their functions, and effectively target them therapeutically. RGS proteins are classified into four subfamilies (R4, R7, RZ, and R12) and function as negative regulators of G protein signaling by inactivating G subunits. We found that the R12 subfamily members RGS10 and RGS14 had lower activity than most R4 subfamily members toward the Gi subfamily member Go. Using structure-based energy calculations with multiple G-RGS complexes, we identified R12-specific residues in positions that are predicted to determine the divergent activity of this subfamily. This analysis predicted that these residues, which we call “disruptor residues,” interact with the G helical domain. We engineered the R12 disruptor residues into the RGS domains of the high-activity R4 subfamily and found that these altered proteins exhibited reduced activity toward Go. Reciprocally, replacing the putative disruptor residues in RGS18 (a member of the R4 subfamily that exhibited low activity toward Go) with the corresponding residues from a high-activity R4 subfamily RGS protein increased its activity toward Go. Furthermore, the high activity of the R4 subfamily toward Go was independent of the residues in the homologous positions to the R12 subfamily and RGS18 disruptor residues. Thus, our results suggest that the identified RGS disruptor residues function as negative design elements that attenuate RGS activity for specific G proteins.
Bibliographical noteFunding Information:
This work was supported by grants from the Israel Science Foundation (grant numbers 1454/13, 1959/13, and 2155/15), the Israel Ministry of Science, Technology and Space, Israel, and the Italian Ministry of Foreign Affairs (3-10704). The authors acknowledge the contribution of COST Action CM-1207 (GLISTEN) to this work.
Copyright © 2018 The Authors, some rights reserved.
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology