SH3 domain tyrosine phosphorylation--sites, role and evolution

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• SH3 domains are critical eukaryotic protein modules involved in signal transduction, proliferation, and cell movement.
• Emerging evidence suggests tyrosine phosphorylation significantly regulates SH3 domain function.

Purpose of the Study:

• To investigate the prevalence and impact of tyrosine phosphorylation on SH3 domains.
• To identify specific phosphorylation sites and sequence motifs within SH3 domains.

Main Methods:

• Utilized the PhosphoSite Plus database to identify tyrosine phosphorylation sites within SH3 domains.
• Performed sequence analysis to delineate conserved phosphorylation motifs.
• Compared the abundance of tyrosine phosphorylation with serine/threonine phosphorylation in SH3, SH2, and WW domains.

Main Results:

• Identified over 100 tyrosine phosphorylations across 20 SH3 domain positions.
• Discovered a conserved ALYD(Y/F) motif associated with the frequently phosphorylated c-Src Tyr-90 site, present in ~15% of human SH3 domains.
• Observed that tyrosine phosphorylation is more prevalent in SH3, SH2, and WW domains than serine or threonine phosphorylation.

Conclusions:

• Tyrosine phosphorylation of SH3 domains acts antagonistically to its role in SH2/PTB domains, inhibiting rather than promoting protein interactions.
• The negatively charged phosphate group interferes with the binding of polyproline helices, thus regulating SH3 domain interactions.
• Tyrosine phosphorylation represents a key regulatory mechanism for SH3 domains and other adaptor domains.