Proton and nitrogen sequential assignments and secondary structure determination of the human FK506 and rapamycin binding protein.

Sequential 1H and 15N assignments of human FKBP, a cytosolic binding protein for the immunosuppressive agents FK506 and rapamycin, are reported. A combination of homonuclear and relayed heteronuclear experiments has enabled assignment of 98 of 99 backbone amide NHs, 119 of 120 C alpha Hs, 97 of 99 non-proline amide 15Ns, and 375 of 412 side-chain resonances of this 107-residue protein. Long-range NOEs are used to demonstrate that FKBP has a novel folding topology consisting of a five-stranded antiparallel beta sheet with +3, +1, -3, +1 loop connectivity.