FIGURE 2.

Probing the interaction of the Cdc34 acidic tail with SCF using a cysteine cross-linking strategy. A, domain organization of human Cdc34 highlighting the amino acid sequence of the acidic tail region responsible for binding to SCF. Three naturally occurring cysteine residues exist in wild-type Cdc34: the active site residue Cys-93, Cys-191, and Cys-227. The mutation of Cys-191 and Cys-227 to serines produces Cdc34 1C. Using Cdc34 1C as a template, eight positions within the acidic tail served as sites for the introduction of a single cysteine residue in the acidic tail. These constructs are collectively referred to as the Cdc34 2C proteins. B, surface representation of a model of Cdc34 docked onto Cul1-Rbx1. The arrow shows the location of the Cul1 basic canyon. C, close-up view of the Cul1 basic canyon. The electrostatic surface potential of Cul1 is shown, where blue indicates the highly positively charged surface of the basic canyon. The positions of five Cul1 residues that have been individually replaced with a cysteine are highlighted as yellow ball-and-stick representations.