Calorimetric and spectroscopic investigation of lactoferrin.

Lactoferrin (LF) is a non-heme iron-binding protein that is a pari of the transferrin protein family, whose relè is to transport iron in blood serum. LF is 80 kDa glycosylated protein of about 700 aminoacids with high homology among species. It is a simple polypeptide chain folded into two symmetrical lobes (N and C lobes), which are highly homologous with each another (33-41% homology). These two lobes are connected by a hinge region containing parts of an a-helix between aminoacids 333 and 343 in human LF. The polypeptide chain includes amino acids 1-332 for the N lobe and 344-703 for the C lobe and is made up of o-helix and (5-sheet structures that create two domains for each lobe (domains I and II). Each lobe can bind a melai atom in synergy with the carbonate ion (CO,2"). LF has a great iron-binding affinity and it is the only transferrin with the ability to hold this metal over a wide pH range, including extremely acidic pH. It also exhibits a great resistance to proteolysis. In addition to these differences, LF's nel positive charge and its distribution in various tissues make it a multifunctional protein. It is involved in severa! physiological functions: regulation of iron absorption in the bowel, immune responso, antioxidant, cariostatic, antianemic, anticarcinogenic, anti-inflammatory properties and protection against microbial infection.