Specific interactions of C-terminal half (C-lobe) of lactoferrin protein with edible sugars: binding and structural studies with implications on diabetes.
Bovine lactoferrin has been shown to reduce the levels of glucose in both normal subjects and non-insulin dependent diabetic patients. The binding studies have shown that various sugar molecules interact with lactoferrin indicating the presence of a sugar-binding site in the protein. Structural studies have revealed that the sugar-binding site is located in the C-terminal half (C-lobe) of bilobal lactoferrin. Since the sugar-binding site was part of the C-lobe, it was better to carry out binding and structural studies using C-lobe rather than the full protein molecule. Therefore, C-lobe was prepared by limited proteolysis of lactoferrin with enzyme proteinase K. It was purified to homogeneity for further studies. The addition of C-lobe to human serum showed significant lowering of glucose levels. The binding studies using C-lobe with nine sugars, glucose, galactose, mannose, xylose, maltose, cellobiose, lactose, sucrose and dextrin gave values of binding constants in the range of 10(-4) to 10(-5)M. The structure determinations of the complexes of C-lobe with all the nine sugars showed that all of them interact with C-lobe through the same recognition site involving several hydrogen bonds and van der Waals interactions.
Mir
Rafia
R
Department of Biophysics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India.
Kumar
Ramasamy Prem
RP
Singh
Nagendra
N
Vikram
Gopalakrishna Pillai
GP
Sinha
Mau
M
Bhushan
Asha
A
Kaur
Punit
P
Srinivasan
Alagiri
A
Sharma
Sujata
S
Singh
Tej P
TP
D000818:Animals; D002417:Cattle; D019422:Dietary Sucrose / Q000737:chemistry*; D019286:Endopeptidase K / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D007781:Lactoferrin / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary
D019422:Dietary Sucrose; D007781:Lactoferrin; D019286:Endopeptidase K