Disclosed is a method for generating a mutein of a protein selected from
the group consisting of human neutrophil gelatinase-associated lipocalin
(hNGAL), rat .alpha..sub.2-microglobulin-related protein (A2m) and mouse
24p3/uterocalin (24p3), said mutein having detectable affinity to a given
target. The method comprises the step of subjecting the protein to
mutagenesis at one or more of the sequence positions which correspond to
the sequence positions 33 to 54, 66 to 83, 94 to 106, and 123 to 136 of
hNGAL, resulting in one or more mutein(s) of the protein. Also disclosed
are muteins obtainable by this method.