The calcium-dependent electrophoretic shift of alpha-lactalbumin, the modifier protein of galactosyl transferase.
alpha-Lactalbumin, the modifier protein of galactosyl transferase in the synthesis of lactose by the mammary gland, has been shown to undergo a Ca2+-dependent electrophoretic shift. Such shifts, characteristic of most calcium modulated proteins, are related to gross conformational changes upon binding calcium when detected in the presence of detergent (SDS-PAGE). However, we detected the calcium shift for alpha-lactalbumin using non-denaturing PAGE (ND-PAGE) where electrical charge changes are observed upon binding calcium. In order for a shift to be observed between the apo and calcium bound protein, calcium ion binding to proteins must have minimal dissociation constants (Kdiss) of 10(-7) M; alpha-lactalbumin is reported to bind calcium at Kdiss = 10(-10) to 10(-12) M. The electrophoretic shift identifies alpha-lactalbumin in complex milk whey patterns of many species of mammals.
Thompson
M P
MP
Eastern Regional Research Center, Philadelphia, Pennsylvania 19118.
Groves
M L
ML
Brower
D P
DP
Farrell
H M
HM
Jenness
R
R
Kotts
C E
CE
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002417:Cattle; D004533:Egtazic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005700:Galactosyltransferases; D006031:Glycosylation; D006736:Horses; D007768:Lactalbumin / Q000378:metabolism; D051379:Mice; D009893:Opossums; D011487:Protein Conformation; D012453:Saimiri; D012589:Sciuridae
D004533:Egtazic Acid; D007768:Lactalbumin; D005700:Galactosyltransferases; D002118:Calcium