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Curr Protein Pept Sci. 2016;17(8):735-745.

Disorder in Milk Proteins: α-Lactalbumin. Part C. Peculiarities of Metal Binding.

Author information

1
Institute for Biological Instrumentation of the Russian Academy of Sciences, Institutskaya str., 7, Pushchino, Moscow region 142290, Russia. epermyak@yandex.ru.
2
Department of Molecular Medicine, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, MDC3540, Tampa, FL 33612, USA. vuversky@health.usf.edu.

Abstract

This is a concluding part of the three-part article from a series of reviews on the abundance and roles of intrinsic disorder in milk proteins. In this paper, we describe the peculiarities of metal binding to a multifunctional milk protein, α-lactalbumin, which has two domains, a large α-helical domain and a small β-sheet domain connected by a calcium binding loop. It is known that in addition to four disulfide bonds, the native fold of this protein is stabilized by binding of a calcium ion. In fact, although in various mammals, α-lactalbumins are rather poorly conserved possessing the overall sequence identity of ~16%, the positions of all eight cysteines and a calcium binding site (residues DKFLDDDITDDI in human protein) are strongly conserved. Curiously, this conserved calcium binding loop is located within a region with increased structural flexibility. Besides canonical calcium binding, α-lactalbumin is known to interact with other metals, such as zinc (for which it has a specific binding site), and, in its apo-form, it can bind other divalent and monovalent cations. The binding of Mg2+, Na+, and K+ to the Ca2+ site increases α-lactalbumin stability against action of heat and various denaturing agents, with the higher stabilization effects being imposed by the stronger bound metal ions.

PMID:
27238572
[Indexed for MEDLINE]

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