Only the reduced conformer of alpha-lactalbumin is inducible to aggregation by protein aggregates.
Reduced apo-alpha-lactalbumin (r-LA) in the pre-molten globule state is soluble in neutral and reduced buffer at 25 degrees C but becomes aggregated when aggregates of various proteins are added. However, protein aggregates do not induce the aggregation of apo-alpha-lactalbumin in the molten globule state. The presence of the molecular chaperone protein disulfide isomerase or the "chemical chaperone" polyethyleneglycol inhibits the induced aggregation. Native proteins, aggregation-free folding intermediates, and soluble aggregates do not induce the aggregation. The interaction between r-LA and protein aggregates is hydrophobic in nature. These findings suggest that pre-molten globule state of LA is the target not only for chaperones but also for protein aggregates.
Li
J
J
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Datun Road, Beijing 100101, China. chihwang@sun5.ibp.ac.cn
Zhang
S
S
Wang
C
C
D000818:Animals; D001059:Apoproteins / Q000737:chemistry*; D002021:Buffers; D002417:Cattle; D007768:Lactalbumin / Q000737:chemistry*; D018832:Molecular Chaperones / Q000737:chemistry*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D019704:Protein Disulfide-Isomerases / Q000737:chemistry* / Q000494:pharmacology; D017510:Protein Folding
D001059:Apoproteins; D002021:Buffers; D018832:Molecular Chaperones; D007768:Lactalbumin; D019704:Protein Disulfide-Isomerases