bi9811664_si_001.pdf (226.39 kB)
Download fileStructure Determination of the Ras-Binding Domain of the Ral-Specific Guanine Nucleotide Exchange Factor Rlf†,‡
journal contribution
posted on 1998-09-05, 00:00 authored by Dirk Esser, Bettina Bauer, Rob M. F. Wolthuis, Alfred Wittinghofer, Robbert H. Cool, Peter BayerRal-specific guanine nucleotide exchange factors RalGDS, Rgl, and Rlf have been suggested
to function as intermediates between Ras and Ral pathways by being able to bind Ras proteins through
their C-terminal Ras-binding domains (RBD). The RBDs of RalGDS and of the Ser/Thr kinase c-Raf-1
have been shown to have the same tertiary structure. In contrast to the RBDs of Raf and RalGDS, which
bind either Ras or Rap with high affinity, Rlf-RBD has a similar affinity for both GTP-binding proteins.
To be able to compare these RBDs on a structural level, we have solved the three-dimensional structure
of Rlf-RBD by NMR spectroscopy. The overall tertiary structure of Rlf-RBD shows the ββαββαβ-fold
of the ubiquitin superfamily and is very similar to that of RalGDS-RBD. The binding interface of Rlf-RBD to Ras was mapped using chemical shift analysis and indicated a binding mode similar to that in the
case of Rap·Raf-RBD. However, comparison of the putatively interacting regions revealed structural
differences which are proposed to be responsible for the different substrate affinities of Rlf-, RalGDS-,
and Raf-RBD.