The chaperone-like alpha-crystallin forms a complex only with the aggregation-prone molten globule state of alpha-lactalbumin.
The chaperone-like alpha-crystallin prevents aggregation of several proteins by interacting with their non-native states. Alpha-Lactalbumin adopts different non-native states under different experimental conditions. We have investigated the interaction of alpha-crystallin with three non-identical non-native states, using fluorescence, circular dichroism, and gel filtration chromatography. The compact molten globule state of apo-alpha-lactalbumin in tris buffer does not interact with alpha-crystallin. The expanded, flexible molten globule-like state of reduced apo-alpha-lactalbumin (formed at pH 7.2) also does not interact with alpha-crystallin. Only the aggregation-prone non-native state of reduced apo-alpha-lactalbumin formed at pH 6.0 interacts with alpha-crystallin to form a stable complex. The alpha-crystallin bound reduced apo-alpha-lactalbumin exhibits properties similar to those of a molten globule. Our results show that alpha-crystallin interacts only with the aggregation prone molten globule state of reduced apo-alpha-lactalbumin but not with the other non-aggregating molten globule states of the protein.
Rajaraman
K
K
Centre for Cellular and Molecular Biology, Hyderabad, India.
Raman
B
B
Ramakrishna
T
T
Rao
C M
CM
D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D002417:Cattle; D002850:Chromatography, Gel; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry* / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007768:Lactalbumin / Q000737:chemistry* / Q000378:metabolism*; D046911:Macromolecular Substances; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D001059:Apoproteins; D003459:Crystallins; D046911:Macromolecular Substances; D018832:Molecular Chaperones; D013439:Sulfhydryl Reagents; C041966:apo-alpha-lactalbumin; D007768:Lactalbumin; D004229:Dithiothreitol