FIGURE 7.

Location of CP43 Trp-365, a site of NFK modification, in the PSII structure from the cyanobacterium, Thermosynechococcus vulcanus (3) (Protein Data Bank code 3ARC). The CP43 protein backbone is shown in yellow, and the D1 and D2 proteins are shown in white and blue, respectively. The Mn₄Ca cluster is displayed in purple and orange; the Tyr_z side chain is shown in blue. Trp residues located within 20 Å of the Mn₄Ca cluster are shown. The side chain of CP43 Trp-365, which is modified to NFK, is shown in red. Trp-359 (CP43), Trp-291 (CP43), and Trp-328 (D2) are shown in green. The measured distances to the Mn₄Ca are 17 Å for Trp-365 (CP43), 16 Å for Trp-359 (CP43), 11 Å for Trp-291 (CP43), and 15 Å for Trp-328 (D2).