Cross-linking of egg white riboflavin-binding protein by calcium phosphate.
No larger molecular weight component appeared in the high-performance gel chromatogram when calcium alone was added to the riboflavin-binding protein solution (RfBP), indicating that calcium alone did not aggregate it. RfBP bound calcium, but the amount of bound calcium decreased markedly upon dephosphorylation. Cross-linked RfBP, which was detected by high-performance gel chromatography using simulated milk ultrafiltrate as the effluent, was formed when calcium and phosphate were added. Cross-linking of RfBP was confirmed by ultracentrifugal analysis. RfBP was found to be cross-linked through its phosphate groups, since no cross-linked fraction was detected when calcium and phosphate were added to a dephosphorylated RfBP solution. RfBP cross-linked by calcium phosphate formed at 12-20 mM calcium, 13-17 mM phosphate, and 10 mM citrate was a dimer, since its retention time was consistent with that of the dimer cross-linked by glyceraldehyde. The physiological function of phosphate groups of RfBP was also discussed.
Aoki
T
T
Department of Biochemical Science and Technology, Faculty of Agriculture, Kagoshima University, Japan.
Yamao
Y
Y
Yonemasu
E
E
Kumasaki
Y
Y
Kako
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002130:Calcium Phosphates / Q000737:chemistry*; D002135:Calcium-Binding Proteins / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry*; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents; D004527:Egg Proteins / Q000737:chemistry; D004529:Egg White; D026901:Membrane Transport Proteins
D002130:Calcium Phosphates; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D004527:Egg Proteins; D026901:Membrane Transport Proteins; C019079:riboflavin-binding protein; D002118:Calcium