A limited set of SH2 domains binds BCR through a high-affinity phosphotyrosine-independent interaction.
SH2 (src homology region 2) domains are implicated in protein-protein interactions involved in signal transduction pathways. Isolated SH2 domains bind proteins that are tyrosine phosphorylated. A novel, phosphotyrosine-independent binding interaction between BCR, the Philadelphia chromosome breakpoint cluster region gene product, and the SH2 domain of its translocation partner c-ABL has recently been reported. We have examined the ability of additional SH2 domains to bind phosphotyrosine-free BCR and compared this with their ability to bind tyrosine-phosphorylated c-ABL 1b. Of 11 individual SH2 domains examined, 8 exhibited relatively high affinity for c-ABL 1b, whereas only 4 exhibited relatively high affinity for BCR. Binding of tyrosine-phosphorylated c-ABL 1b by the relatively high-affinity ABL and ARG SH2 domains was quantitatively analyzed, and equilibrium dissociation constants for both interactions were estimated to be in the range of 5 x 10(-7) M. The ABL SH2 domain exhibited relatively high affinity for phosphotyrosine-free BCR as well; however, this interaction appears to be about two orders of magnitude weaker than binding of tyrosine-phosphorylated c-ABL 1b. The ARG SH2 domain exhibited relatively weak affinity for BCR and was determined to bind about 10-fold less strongly than the ABL SH2 domain. The ABL and ARG SH2 domains differ by only 10 of 91 amino acids, and the substitution of ABL-specific amino acids into either the amino- or carboxy-terminal half of the ARG SH2 domain was found to increase its affinity for BCR. We discuss these results in terms of a model which has been proposed for peptide binding by class I histocompatibility glycoproteins.
Muller
A J
AJ
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024.
Pendergast
A M
AM
Havlik
M H
MH
Puil
L
L
Pawson
T
T
Witte
O N
ON
D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000378:metabolism*; D019000:Phosphotyrosine; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism; D051562:Proto-Oncogene Proteins c-bcr; D016392:Proto-Oncogene Proteins pp60(c-src); D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D016315:Proto-Oncogene Proteins c-abl; D016392:Proto-Oncogene Proteins pp60(c-src); D051562:Proto-Oncogene Proteins c-bcr