Phylogenetic variations in the calcium-dependent electrophoretic shift of alpha-lactalbumin.
alpha-Lactalbumin undergoes a calcium-dependent electrophoretic shift at pH 8.3. When Ca2+ is removed by a chelator, the mobility of the protein increases, reflecting the exposure of negative electrical charges. The shift, however, is not observed by electrophoresis in the presence of SDS, which demonstrates that alpha-lactalbumin does not undergo a measurable conformational change upon debinding of Ca2+. Relative electrophoretic mobilities vary from 1.0 (no shift) to 1.4 among alpha-lactalbumins of different orders of mammals. The differences suggest a variable number of gram atoms of Ca2+ bound to alpha-lactalbumin or substitution of amino acid Ca2+ ligands in the calcium-binding loop.
Thompson
M P
MP
US Department of Agriculture, Eastern Regional Research Center, Philadelphia, PA 19118.
Brower
D P
DP
Jenness
R
R
Kotts
C E
CE
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000032:analysis / Q000378:metabolism*; D008894:Milk Proteins / Q000032:analysis; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010802:Phylogeny; D000067816:Whey Proteins
D008894:Milk Proteins; D000067816:Whey Proteins; D007768:Lactalbumin; D002118:Calcium