Substrate recognition component of a SCF (SKP1-CUL1-F-box protein) E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins. Probably recognizes and binds to phosphorylated target proteins (By similarity). Protein modification; protein ubiquitination. Interacts with SKP1. Component of the probable SCF(YDR131C) complex containing CDC53, SKP1, RBX1 and YDR131C.