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Role of Residue 43 in Activation of RhoA, RhoB, and RhoC
Author(s) -
Peters Justin P.,
Ellerbroek Shawn M.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.lb26-a
Subject(s) - rhoa , rhob , guanine nucleotide exchange factor , rhoc , gtpase , microbiology and biotechnology , biochemistry , biology , signal transduction
Rho family GTPases are mediators of cell proliferation, migration, and transformation. The three isoforms RhoA, RhoB, and RhoC share over 80% sequence identity. It is not fully understood why three such closely related Rho GTPases exist, but part of the answer may lie with a class of enzymes that activate Rho proteins called guanine nucleotide exchange factors (GEFs). In a previous study, we observed selective activation of RhoA and RhoB by a novel GEF called XPLN. Further, a variation in amino acid 43 between RhoC (isoleucine) and RhoA and RhoB (valine) was implicated as a structural impediment to XPLN activation of RhoC. In work presented here, we confirm and extend the above observation to include multiple GEFs (VAV2, XPLN, Dbs, GEFT, and Dbl) through in vitro analysis of exchange factor activity of normal Rho proteins and those mutated at residue 43. We conclude that mutation of RhoA (V43I) significantly increases both basal and GEF‐stimulated nucleotide exchange. Mutation of RhoB (V43I) did not affect basal nucleotide exchange, but impaired all GEF catalyzed exchange, with XPLN, Dbs, and Dbl consistently exhibiting greater sensitivity to the residue shift than VAV2 and GEFT. The mutation of RhoC (I43V) did not affect basal nucleotide exchange and rendered the GTPase a better substrate for all GEFs examined. These findings suggest residue 43 of RhoA, RhoB, and RhoC is a determinant of both GEF activity and selectivity.