Pressure-induced conformational changes of beta-lactoglobulin by variable-pressure Fourier transform infrared spectroscopy.
Pressure-induced conformational changes in D(2)O solutions of the two genetic variants of beta-lactoglobulin A (beta-lg A) and beta-lactoglobulin B (beta-lg B) and an equal mixture of both variants (beta-lg A+B) were studied by employing variable-pressure Fourier transform infrared (VP-FTIR) spectroscopy. Changes in the secondary structure of beta-lg A were observed at lower pressure compared to beta-lg B, indicating that beta-lg A had a more flexible structure. During the decompression cycle beta-lg A showed protein aggregation, accompanied by an increase in alpha-helical conformation. The changes in the secondary structure of beta-lg B with the pressure were minor and for the most part reversible. Upon decompression no aggregation in beta-lg B was observed. Increasing the pressure from 0.01 to 12.0 kbar of a solution containing beta-lg A+B resulted in substantial broadening of all major amide I bands. This effect was partially reversed by decreasing the hydrostatic pressure. beta-lg A+B underwent less aggregate formation than beta-lg A, possibly as a result of protein-protein interactions between beta-lg A and beta-lg B. Hence, it is likely that the functional or biological attributes of beta-lg proteins may be affected in different ways by hydrostatic pressure.
Hosseini-nia
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School of Dietetics and Human Nutrition and Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, Quebec, Canada.
Ismail
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Kubow
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D003903:Deuterium; D007782:Lactoglobulins / Q000737:chemistry*; D011312:Pressure; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared
D007782:Lactoglobulins; D003903:Deuterium