IndraLab
Statements
sparser
"To test the extent to which the formation of Grb2-Sos1 complex with a 2:1 stoichiometry may be influenced by steric hindrance, we next measured the binding of full-length Grb2 to various single, double and triple mutant constructs of the PR domain, mutated with respect to one or more of the S1–S4 sites ( xref and xref )."
sparser
"Based on the concentrations used for these studies, it is estimated that the affinity of SOS1 scrambled for GRB2 is greater than 50 µM. These experiments suggest that the PxxPxR motifs or sequences needed for interactions with these motifs in the context of short peptides are not required for the high-affinity binding of GRB2 to SOS1."
sparser
"Given that the formation of Sos1-Grb2-Gab1 ternary signaling complex proceeds in a non-competitive manner [ xref ], the most straightforward interpretation of these salient observations is that the Sos1 peptide binds only to the nSH3 domain but not the cSH3 domain, while the Gab1 peptide binds only to the cSH3 domain in the context of full-length Grb2."
sparser
"While we have relied here on short peptides to mimic Sos1 and Gab1, due largely to inherent difficulties associated with isolation and purification of full-length Sos1 and Gab1 proteins, it should be noted that these peptides suffice par excellence for studying the binding of Sos1 and Gab1 to Grb2 using biophysical methods."
sparser
"Although these CD measurements are of highly qualitative nature and thus do not provide the physical basis of how the binding of Sos1 to the nSH3 domain may trigger a conformational change within Grb2 such that the nSH3 domain is only accessible to Gab1, the fact that Grb2 appears to be a highly flexible molecule by virtue of its ability to undergo discernable secondary and tertiary structural changes upon binding to Sos1 and Gab1 peptides nonetheless supports the notion that allostery is likely to play a central role in mediating communication between the nSH3 and cSH3 domains so as to allow the assembly of Sos1-Grb2-Gab1 ternary signaling complex in a non-competitive manner."
sparser
"Although efforts by others and us directed at the determination of X-ray or NMR structures of full-length Grb2 bound to Sos1 or Gab1 constructs of any sort over the past decade or so have met no success, presumably due to the transient nature of Sos1-Grb2-Gab1 complex, we have nonetheless made an attempt here to create a crude 3D structural model of how the binding of one molecule of Sos1 to the nSH3 domain may allosterically induce a conformational change within Grb2 such that the loading of a second molecule of Sos1 onto the cSH3 domain is blocked and, in so doing, allowing Gab1 access to the cSH3 domain in an exclusively non-competitive manner to generate the Sos1-Grb2-Gab1 ternary complex ( xref )."
sparser
"These observations fit well with previous studies showing that SOS1 peptides bind to individual SH3 domains from GRB2 with affinities ranging from 20 µM to 1 mM [ xref – xref ], while the affinity for the binding of full-length GRB2 with full-length SOS1 or the complete PRR of SOS1 and CBL is between 300 and 400 nM ( xref ) and [ xref – xref ]."
reach
"A large number of these PPIs are mediated by multiple SLiM classes or SLiM instances, for example, in the interaction between GRB2 (uniprot : P62993) and SOS1 (uniprot : Q07889); SOS1 has seven putative SH3 motifs and GRB2 has two SH3 domains, potentially this can equate to 14 binding interfaces for a single PPI."