Fluorescence contributions of the individual Trp residues in goat alpha-lactalbumin.

Goat alpha-lactalbumin (GLA) contains four tryptophan (Trp) residues. In order to obtain information on the fluorescence contribution of the individual Trp residues in native GLA, we recorded the fluorescence spectra of four GLA mutants, W26F, W60F, W104F, and W118F, in each of which a single Trp residue was replaced with phenylalanine (Phe). Comparison of the fluorescence spectra of the four mutants with that of wild-type GLA indicated that, in native GLA, three Trp residues (Trp60, Trp104, and Trp118) are strongly quenched and account for the partial indirect quenching of Trp26.

Selectivity of tryptophan residues in mediating photolysis of disulfide bridges in goat alpha-lactalbumin.

Goat alpha-lactalbumin (GLA) contains four tryptophan (Trp) residues and four disulfide bonds. Illumination with near-UV light results in the cleavage of disulfide bridges and in the formation of free thiols. To obtain information about the reaction products, the illuminated protein was carbamidomethylated and digested with trypsin and the peptides were analyzed by mass spectrometry.

Influence of Trp mutation on native, intermediate, and transition states of goat alpha-lactalbumin: an equilibrium and kinetic study.

Equilibrium circular dichroism and kinetic stopped-flow fluorescence studies on the stability and the folding kinetics of a set of Trp to Phe mutants of goat alpha-lactalbumin (GLA) were used to characterize the native, intermediate, and transition states of these constructs. GLA contains four tryptophan residues, three of which, Trp26, Trp104, and Trp118, are located in the alpha-domain, while the fourth, Trp60, is located in the beta-domain. Trp26, Trp60, and Trp104 are part of a hydrophobic cluster, whereas Trp118 is situated in a more flexible region near the C-terminal end of the protein.

Tryptophan to phenylalanine substitutions allow differentiation of short- and long-range conformational changes during denaturation of goat alpha-lactalbumin.

To test the occurrence of local particularities during the unfolding of Ca2+-loaded goat alpha-lactalbumin (GLA) we replaced Trp60 and -118, either one or both, by Phe. In contrast with alternative studies, our recombinant alpha-lactalbumins are expressed in Pichia pastoris and do not contain the extra N-terminal methionine. The substitution of Trp60 leads to a reduction of the global stability.

Photoexcitation of tryptophan groups induces reduction of two disulfide bonds in goat alpha-lactalbumin.

Illumination of goat alpha-lactalbumin (GLA) with 280 or 295 nm light results in tryptophan-mediated photolysis of disulfide bonds within the protein. The photolysis is not dependent on the absence or presence of Ca(2+) and is observed as well on illumination of native and of partially unfolded GLA. However, photolysis of native GLA results in a partial unfolding of the protein.

Structural basis for difference in heat capacity increments for Ca(2+) binding to two alpha-lactalbumins.

Thermodynamic parameters for the unfolding of as well as for the binding of Ca(2+) to goat alpha-lactalbumin (GLA) and bovine alpha-lactalbumin (BLA) are deduced from isothermal titration calorimetry in a buffer containing 10 mM Tris-HCl, pH 7.5 near 25 degrees C. Among the different parameters available, the heat capacity increments (Delta C(p)) offer the most direct information for the associated conformational changes of the protein variants.

[Non-Hodgkin's lymphoma: unusual testicular localization: case report].

We report on a 58-year-old man, in whom a clinical suspicion of orchitis of the right testicle was treated with antibiotics. The instored antibiotics failed to improve the clinical condition of orchitis. Previous medical history revealed a gastric lymphoma for which gastrectomy was performed, followed by combination chemotherapy.