Structural basis for specificity switching of the Src SH2 domain.
The Src SH2 domain binds pYEEI-containing phosphopeptides in an extended conformation with a hydrophobic pocket, which includes ThrEF1, binding Ile(pY +3). Mutating ThrEF1 to tryptophan switches specificity to an Asn(pY +2) requirement, yielding a biological mimic of the Grb2 SH2 domain. Here we show that the Src ThrEF1Trp SH2 domain mutant binds pYVNV phosphopeptides in a beta turn conformation, which, despite differing conformations of the interacting tryptophan, closely resembles the native Grb2/pYVNV cognate peptide binding mode. The ThrEF1Trp substitution therefore switches specificity by physically occluding the pTyr +3 binding pocket and by providing additional interaction surface area for Asn(pY +2). This demonstrates structurally how novel SH2 domain specificities may rapidly evolve through single amino acid substitutions and suggests how new signaling pathways may develop.
Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada.
M S
MS
Kimber
J
J
Nachman
A M
AM
Cunningham
G D
GD
Gish
T
T
Pawson
E F
EF
Pai
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D000081247:CSK Tyrosine-Protein Kinase; D002645:Chickens; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D051380:GRB2 Adaptor Protein; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013379:Substrate Specificity; D018909:src Homology Domains / Q000235:genetics; D019061:src-Family Kinases
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; D008024:Ligands; D010748:Phosphopeptides; D011506:Proteins; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases