>3r21A (A:) observed residues (from ATOM records)
qwaledfeigrplgkgkfgnvylarekqskfilalkvlfkaqlekagvehqlrreveiqs
hlrhpnilrlygyfhdatrvylileyaplgtvyrelqklskfdeqrtatyitelanalsy
chskrvihrdikpenlllgsagelkiadfgwsvlcgtldylppemiegrmhdekvdlwsl
gvlcyeflvgkppfeantyqetykrisrveftfpdfvtegardlisrllkhnpsqrpmlr
evlehpwitanssk