PERQ1 is a 1,035 amino acid phosphoprotein that contains one GYF domain and belongs to the PERQ family. Ubiquitously expressed, PERQ1 exhibits highest expression in brain and lung, followed by heart, spleen and kidney. PERQ1 contains a GYF domain in its N-terminal half and a clathrin light chain homology domain in its C-terminal half. PERQ1 interacts with GRB10, with transient binding increased under IGF-I stimulation, thereby leading to recruitment of the PERQ1/GRB10 complex to the IGF-I receptor. PERQ1 may also increase IRS-1, Shc and IGF-I receptor phosphorylation during IGF-I stimulation, and may act cooperatively with GRB10 to regulate tyrosine kinase receptor signaling.