The chtA gene codes for a protein with F-box and WD40 repeats: the diagram (A Upper) shows the relative positions of the F-box and the WD40 repeats (gray). GenBank accession nos. are AF151111 and AF151112 for chtA. The insertion site of pBSR3 in chtA is shown. The position of the primer used for 5′ rapid amplification of cDNA ends experiments is indicated by an arrow. The sequence is shown with the F-box (dark gray) and WD40 repeats in lighter gray and underlined. B shows the homology with several other F-box sequences: humans (skp2, accession no. AAC50242) (51), C. elegans (sel10, accession no. AF020788) (14), and S. cerevisiae (met30, accession no. P39014) (52, 53).