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.
Kimber
M S
MS
Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada.
Nachman
J
J
Cunningham
A M
AM
Gish
G D
GD
Pawson
T
T
Pai
E F
EF
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