Premium
Activation of the exchange factor Ras‐GRF by calcium requires an intact Dbl homology domain
Author(s) -
Freshney Norman W.,
Goonesekera Sunali D.,
Feig Larry A.
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)00309-8
Subject(s) - calcium , chemistry , homology (biology) , biophysics , domain (mathematical analysis) , microbiology and biotechnology , biochemistry , biology , amino acid , mathematics , mathematical analysis , organic chemistry
Ras‐GRF is a guanine nucleotide exchange factor that activates Ras proteins. Its activity on Ras in cells is enhanced upon calcium influx. Activation follows calcium‐induced binding of calmodulin to an IQ motif near the N‐terminus of Ras‐GRF. Ras‐GRF also contains a Dbl homology (DH) domain C‐terminal to the IQ motif. In many proteins, DH domains act as exchange factors for Rho‐GTPase family members. However, we failed to detect exchange activity of this domain on well characterized Rho family members. Instead, we found that mutations analogous to those that block exchange activity of Dbl prevented Ras‐GRF activation by calcium/calmodulin in vivo. All DH domains are followed immediately by a pleckstrin homology (PH) domain. We found that a mutation at a conserved site within the PH domain following the DH domain also prevented Ras‐GRF activation by calcium in vivo. These results suggest that in addition to playing a role as activators of Rho proteins, DH domains can also contribute to the coupling of cellular signals to Ras activation.