Determination of the sequence which spans the beginning of the insertion region in Anacystis nidulans flavodoxin.

Anacystis nidulans flavodoxin is one of the long chain flavodoxins (Mayhew & Ludwig, 1975). Comparisons of its structure with the structures of shorter chain species (main text: Ludwig et al., 1982) show that in A. nidulans flavodoxin most of the extra residues occupy a region adjoining the third helix and the fifth strand of parallel sheet. The sequences of peptides isolated after cyanogen bromide cleavage and after digestion with Staphylococcus aureus protease, reported here, fit into the electron density map of A. nidulans flavodoxin, starting near the middle of the third helix, and verify that the major insertion interrupts the fifth strand of parallel sheet.