ADENOSINE-DEAMINASE IS A SPECIFIC PARTNER FOR THE GRB2 ISOFORM GRB3-3

Grb3-3 is an isoform of Grb2, thought to arise by alternative splicing , that lacks a functional SH2 domain but retains functional SH3 domain s, which allow interaction with other proteins through binding to prol ine-rich sequences. Several evidences suggest that besides common part ners for Grb2 and Grb3-3, specific targets could exist. In order to fi nd specific partners for Grb3-3, we have screened a human cDNA library by the yeast two-hybrid system with Grb3-3 as a bait. We have identif ied adenosine deaminase, an enzyme involved in purine metabolism whose deficiency is associated with severe combined immunodeficiency, as a Grb3-3 binding protein that is not able to bind to Grb2. This interact ion has been confirmed in vitro with GST fusion proteins and in vivo b y coimmunoprecipitation experiments in NIH3T3 cells stably transfected with Grb3-3. The functional significance of this finding is discussed . (C) 1997 Academic Press.