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Comparison of Holo-and Apo-Lactalbumin |
Alpha-Lactalbumin regulates the
lactose synthase complex. This complex then catalyses the synthesis
of lactose in the mammary glands when lactation occurs. The native
structure of α -Lactalbumin
consists of two sub-domains, α-domain and the β-domain, that are
divided by a cleft. The α-domain has four α-helices and two short 310
helices. The β-domain contains a triple-stranded anti-parallel
β-sheet, a 310 helix and various loops.
Wire Frame
Lactalbumin with Calcium and TRP
Backbone
Disulfide Bonds (4)
Backbone and sidechains
Cartoon, Hbonds and Wireframe
Comparison of Apo- and Holo- lactalbumin
The
structural comparison of the apo vs. holo form of the protein was
obtained at high ionic strength thus the structures appear more
similar than they are. High ionic strength was required to isolate
the apo form of the protein, which is more unstable than the holo
form, because the calcium ligand is absent. Studies have shown that
the high affinity of α-Lactalbumin for calcium is due to the fact
that the electrostatic interactions of calcium with the binding site
residues stabilizes the native form of the protein. The actual
differences is secondary structure of the apo- and holo- form of the
protein are limited to the active site domain.
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