Structural evidence for the presence of a secondary calcium binding site in human alpha-lactalbumin.
The high-resolution X-ray crystal structure of human alpha-lactalbumin (at 1.8 A) in the presence of an elevated level of calcium reveals a new secondary calcium binding site, 7.9 A away from the primary calcium binding site known in all alpha-lactalbumin structures so far. The new calcium binding site is different from the zinc and sulfate binding sites [Ren, J., et al. (1993) J. Biol. Chem. 268, 19292-19298] but shares common features with the manganese binding site as described by Gerkin [Gerkin, T. A. (1984) Biochemistry 23, 4688-4697]. The proximity of the manganese and calcium binding region and the location of the functional site on one side of the charged surface of the alpha-lactalbumin molecule suggest that these binding sites might play a role in the formation of the lactose synthase complex.
Chandra
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Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K.
Brew
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Acharya
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D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D007768:Lactalbumin / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D055672:Static Electricity
D007768:Lactalbumin; D002118:Calcium