Calcium-regulated interactions of human alpha-lactalbumin with bee venom melittin.
Affinity chromatography, fluorescence and circular dichroism spectroscopy methods have been used to study the interaction of melittin, a 26-residue peptide from bee venom, with Ca2(+)-binding alpha-lactalbumin from human milk. It has been revealed that melittin binds to the apo- and acidic states of alpha-lactalbumin while the presence of Ca2+ makes the interaction essentially weaker. The association constant for the complex of melittin with apo-alpha-lactalbumin determined from spectropolarimetric melittin-titration data is 2 X 10(7) M-1. The complexation of alpha-lactalbumin with melittin decreases its affinity to Ca2+ by three orders of magnitude. The interaction of apo-alpha-lactalbumin with melittin causes some changes in the environment of its aromatic amino acid residues and drastically alters the conformation of melittin, increasing its alpha-helical content but leaving its single tryptophan residue accessible to water. In the case of the acidic state of alpha-lactalbumin the interaction does not induce an increase in alpha-helical content of melittin.
Permyakov
E A
EA
Institute of Biological Physics, U.S.S.R. Academy of Sciences, Pushchino, Moscow Region.
Grishchenko
V M
VM
Kalinichenko
L P
LP
Orlov
N Y
NY
Kuwajima
K
K
Sugai
S
S
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002942:Circular Dichroism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D007768:Lactalbumin / Q000378:metabolism*; D008555:Melitten / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D014364:Tryptophan; D015032:Zinc / Q000378:metabolism
D008555:Melitten; D014364:Tryptophan; D007768:Lactalbumin; D015032:Zinc; D002118:Calcium