Abstract
Conformational changes of bovine α-lactalbumin in sodium dodecyl sulfate (SDS) solution were studied with the circular dichroism (CD) method using a dilute phosphate buffer ofpH 7.0 and ionic strength 0.014. The proportions of α-helix and β-structure in α-lactalbumin were 34% and 12%, respectively, in the absence of SDS. In the SDS solution, the helicity increased to 44%, while the β-structure disappeared. In order to verify the structural change from β-structure to α-helix, the moiety, assuming the β-structure in the α-lactalbumin, was isolated by a chymotryptic digestion. The structure of this α-lactalbumin fragment, Phe31-Ile59, was almost disordered. However, the fragment adopted a considerable amount of α-helical structure in the SDS solution. On the other hand, the tertiary structure of α-lactalbumin, detected by changes of CD in the near-ultraviolet region, began to be disrupted before the secondary structural change in the surfactant solution. Dodecyl sulfate ions of 80 mol were cooperatively bound to α-lactalbumin. Although the removal of the bound dodecyl sulfate ions was tried by the dialysis against the phosphate buffer for 5 days, 4 mol dodecyl sulfates remained per mole of the protein. The remaining amount agreed with the number of stoichiometric binding site, determined by the Scatchard plot, indicating that the stoichiometric binding was so tight.
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Acharya, K. R., Stuart, D. I., Walker, N. P. C., Lewis, M., and Phillips, D. C. (1989).J. Mol. Biol. 208 99–127.
Acharya, K. R., Stuart, D. I., Phillips, D. C., and Scheraga, H. A. (1990).J. Protein. Chem. 9 549–563.
Bruning, W., and Holtzer, A. (1961).J. Am. Chem. Soc. 83 4865–4866.
Chen, Y. H., Yang, J. T., and Chau, K. H. (1974).Biochemistry 13 3350–3359.
Fraenkel-Conrat, H., Harris, J. I., and Levy, A. L. (1954). InMethods of Biological Analysis Interscience, New York, Vol. 2, pp. 359–425.
Greenfield, N., and Fasman, G. D. (1969).Biochemistry 8 4108–4116.
Koga, K., and Berliner, L. J. (1985).Biochemistry 24 7257–7262.
Kuwajima, K., Hiraoka, Y., Ikeguchi, M., and Sugai, S. (1985).Biochemistry 24 874–881.
Kuwajima, M., Ikeguchi, M., Sugawara, T., Hiraoka, Y., and Sugai, S. (1990).Biochemistry 29 8240–8249.
Lala, A. K., and Kaul, P. (1992).J. Biol. Chem. 267 19,914–19,918.
Herskovits, T. T., SanGeorge, R. C., and Cavanagh, S. M. (1978).J. Colloid Interface Sci. 63 226–234.
Hiraoka, Y., Segawa, T., Kuwajima, K., Sugai, and Murai, N. (1980).Biochem. Biophys. Res. Commun. 95 1098–1104.
Ikeguchi, M., Kuwajima, K., and Sugai, S. (1986).J. Biochem. 99 1191–1201.
Jones, M. N. (1975). InBiological Interfaces, Elsevier, Amsterdam, pp. 101–130.
Lapanje, S. (1978). InPhysicochemical Aspects of Protein Denaturation, Wiley-Interscience, New York, pp. 156–179.
Nozaki, Y., and Tanford, C. (1963).J. Biol. Chem. 238 4074–4078.
Nozaki, Y., and Tanford, C. (1970).J. Biol. Chem. 245 1648–1652.
Parker, W., and Song, P. S. (1992).Biophys. J. 61 1435–1439.
Steinhardt, J., and Reynolds, J. A. (1969). InMultiple Equilibria in Proteins, Academic Press, New York, pp. 239–302.
Takeda, K., Miura, M., and Takagi, T. (1981).J. Colloid Interface Sci. 82 38–44.
Takeda, K., Shigeta, M., and Aoki, K. (1987).J. Colloid Interface Sci. 117 120–126.
Takeda, K., Sasa, K., Kawamoto, K., Wada, A., and Aoki, K. (1988a).J. Colloid Interface Sci. 124, 284–289.
Takeda, K., Wada, A., Yamamoto, K., Hachiya, K., and Batra, P. P. (1988b).J. Colloid Interface Sci. 125 307–313.
Takeda, K., Sasa, K., Nagao, M., and Batra, P. P. (1988c).Biochim. Biophys. Acta 957 340–344.
Takeda, K., and Moriyama, Y. (1990).J. Protein. Chem. 9 573–582.
Takeda, K., Sasaoka, H., Sasa, K., Hirai, H., Hachiya, K., and Moriyama, Y. (1992).J. Colloid Interface Sci. 154 385–392.
Wada, A., and Takeda, K. (1990).J. Colloid Interface Sci. 138 277–279.
Yang, J. T., Wu, C.-S. C., and Martinez, H. M. (1986). InEnzyme Structure, Part K (C. H. W. Hirs and S. N. Timasheff, eds.),Methods in Enzymology Academic Press, San Diego, Vol. 130, pp. 208–269.
Yonath, A., Podjarny, A., Honig, B., Sielecki, A., and Traub, W. (1977).Biochemistry 16 1418–1424.
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Hamada, S., Takeda, K. Conformational changes of α-lactalbumin and its fragment, Phe31-Ile59, induced by sodium dodecyl sulfate. J Protein Chem 12, 477–482 (1993). https://doi.org/10.1007/BF01025048
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DOI: https://doi.org/10.1007/BF01025048