The detection of four molecular forms of human transferrin during the iron binding process

Abstract. Lactoferrin is a non-heme protein known for its ability to bind tightly Fe(III) ions in various physiological environments. Due to this feature lactoferrin plays an important role in the processes of iron regulation at the cellular level preventing the body from damages produced by high levels of free iron ions. The X-ray crystal structure of human lactoferrin shows that the iron-binding process leads to conformational changes within the protein structure. The present study was addressed to conformation stability of human lactoferrin in solution. Using molecular dynamics simulations, it was shown that Arg121 is the key amino acid in the stabilization of the Fe(III) ion in the N-lobe of human lactoferrin. The small-angle neutron scattering method allowed us to detect the structural differences between the open and closed conformation of human lactoferrin in solution. Our results indicate that the radius of gyration of apolactoferrin appears to be smaller than that of the hololactoferrin, $R_{g}=24.16(\pm 0.707)$ R g = 24 . 16 ( ± 0 . 707 ) Å and $R_{g}= 26.20(\pm 1.191)$ R g = 26 . 20 ( ± 1 . 191 ) Å, respectively. The low-resolution three-dimensional models computed for both forms of human lactoferrin in solution also show visible differences, both having a more compact conformation compared to the high-resolution structure. Graphical abstract

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Iron-Binding Process in the Amino- and Carboxyl-Terminal Lobes of Ovotransferrin: Quantitative Studies Utilizing Single Fe3+-Binding Mutants

Biochemistry ◽

10.1021/bi049147j ◽

2004 ◽

Vol 43 (34) ◽

pp. 11118-11125 ◽

Cited By ~ 7

Author(s):

Ikuko Okamoto ◽

Kimihiko Mizutani ◽

Masaaki Hirose

Keyword(s):

Iron Binding ◽

Binding Process ◽

Quantitative Studies ◽

Carboxyl Terminal

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Multiple molecular forms of human lactoferrin. Identification of a class of lactoferrins that possess ribonuclease activity and lack iron-binding capacity.

Journal of Experimental Medicine ◽

10.1084/jem.170.2.415 ◽

1989 ◽

Vol 170 (2) ◽

pp. 415-429 ◽

Cited By ~ 75

Author(s):

P Furmanski ◽

Z P Li ◽

M B Fortuna ◽

C V Swamy ◽

M R Das

Keyword(s):

Binding Capacity ◽

Molecular Forms ◽

Major Constituent ◽

Iron Binding ◽

Multiple Molecular Forms ◽

Polyclonal Antisera ◽

Terminal Amino ◽

Iron Binding Capacity ◽

Regulatory Functions ◽

Binding Component

Lactoferrin (Lf), the major iron-binding component of milk, also a major constituent of the specific granules of neutrophils involved in antimicrobial activity and a glycoprotein thought to play a role in regulatory functions in the hematopoietic system as well as other physiologic activities, is shown to occur in three isoforms. One, Lf-alpha, binds iron; the other two, Lf-beta and Lf-gamma, express potent RNase activity, but do not bind iron. The three isoforms are very similar or identical in Mr, pI, partial proteolytic peptide patterns, NH2-terminal amino acid sequence, and reactivity with mAbs and polyclonal antisera against the RNase and Lf, respectively. The finding of structurally similar but enzymatically distinct forms of Lf may be related to the diverse functions of the molecule.

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