Identification of residues essential for progesterone binding to uteroglobin by site-directed mutagenesis

The Crystal Structure of the Major Cat Allergen Fel d 1, a Member of the Secretoglobin Family

“…It has been demonstrated that uteroglobin is a carrier of small ligands such as polychlorinated biphenyl derivatives, phosphatidyl inositol, phosphatidyl choline, retinol, and progesterone (41,47,49). The tyrosine residue Tyr-21 is involved in the binding of ligands to uteroglobin (41), and the mutation of this position to alanine or phenylalanine results in a dramatic decrease of progesterone binding to uteroglobin (52). The particular distribution of residues in the cavity of Fel d 1 provides an amphipathic character to the cavity, which may be related to the physicochemical properties of the endogenous ligand.…”

CD studies of peptides that mimic the four helicoidal sequences of the uteroglobin monomer

“…The peptide-spanning helix III, according to the structure of uteroglobin in the crystal form P21, UTG(29-45), showed a percentage of helicity (67%; Fig. 3, left) higher than those found for UTG (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) and UTG (17)(18)(19)(20)(21)(22)(23)(24), which could be explained in terms of the relative lengths of the peptides. However, in contrast to what was observed for UTG(3-16) compared to UTG (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) and for UTG(17-28) compared to UTG (17)(18)(19)(20)(21)(22)(23)(24), the prolongation of UTG(29-45) by the addition of two amino acids at the C-terminal position (UTG(29-47)) provoked a decrease in the percentage of helicity (57%; Fig.…”

“…The addition of the two first N-terminal residues of the uteroglobin monomer to UTG (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) seemed to inhibit to some extent the formation of aggregates, as shown in Fig. 4 (right) for UTG- (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14).…”

“…UTG (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), the shortest fragment containing helix I in both crystalline forms (see Table 1), reached a maximum of 53% helicity in the presence of HFIE while UTG(3-16) was more helicoidal (68%; Fig. 2, left).…”

“…1; the picture was generated with MOL-SCRIPT [13]). The progesterone-protein complex has never been isolated, but experiments carried out in vitro with the protein and some analogues have shown that Tyr 2', Thr 6° [14] and His 8 [15][16][17] are crucial for binding and that disulfide bridges play an essential role, controlling the entrance of the steroid to the channel through which the hydrophobic cavity can be reached [18]. The particular tertiary structure of uteroglobin and the fact that the mechanism of complexation remains unsolved moved us to start studying this protein.…”