Fig. 3. Structure of the PP1c–RVxF-containing-peptide complex. PP1c is shown as a ribbon structure, and residues RRVSFA of the peptide are shown as green sticks with positively charged groups in blue and negatively charged groups in red. The GM peptide lies in a groove running parallel to the ß-strand ß14 (Leu289 –Leu296). The N-terminal arginine residue of the peptide is close to a negatively charged region that is likely to bind to other basic residues that are often found N-terminal to RRVxF. This negatively charged region on PP1c encompasses Glu54, Glu56, Asp166, and Glu67, which are involved in binding to the 12IKGI15 motif of I-2. The phosphate analogue tungstate is shown at the catalytic site. The ß12-ß13 loop containing Cys273 that covalently binds to microcystin is indicated in yellow. The figure was kindly produced by David Barford from the crystal structure of the PP1c-GM[63-75] peptide complex presented at the 1996 FASEB conference on protein phosphatases (Egloff et al., 1997).
