Cover photograph (Copyright © 2001, American Society for Microbiology. All rights reserved.): The structural model for the leucine-rich repeat (LRR) of Grr1 predicts the existence of a positively charged concave surface. A C trace of the LRR domain (dark gray) is a tube overlaid on the LRR molecular surface. Red and blue represent negatively and positively charged regions of that domain, respectively. Mutations predicted to neutralize the positively charged residues on the convave surface (green) or to convert them to negatively charged residues interfere with the capacity of Grr1 to recognize and bind to phosphorylated substrates. Consequently, targets of SCF^Grr1, such as the G₁ cyclin Cln2, are stabilized in such mutants. (See related article on page 2506.)