Influence of iron binding in the structural stability and cellular internalization of bovine lactoferrin

Barros, Caroline Augusto; Sanches, Daniel; Marques de Carvalho, Carlos Alberto; Santos, Ronimara Aparecida; Ferraz de Souza, Theo Luiz; Macena Leite, Vitor Luis; Pereira da Costa Campos, Samir; Cheble de Oliveira, Andréa; Gonçalves, Rafael Braga

Lactoferrin (Lf) is an iron-binding glycoprotein and a component of many external secretions with a wide diversity of functions. Structural studies are important to understand the mechanisms employed by Lf to exert so varied functions. Here, we used guanidine hydrochloride and high hydrostatic pressure to cause perturbations in the structure of bovine Lf (bLf) in apo and holo (unsaturated and iron-saturated, respectively) forms, and analyzed conformational changes by intrinsic and extrinsic fluorescence spectroscopy. Our results showed that the iron binding promotes changes on tertiary structure of bLf and increases its structural stability. In addition, we evaluated the effects of bLf structural change on the kinetics of bLf internalization in Vero cells by confocal fluorescence microscopy, and observed that the holo form was faster than the apo form. This finding may indicate that structural changes promoted by iron binding may play a key role in the intracellular traffic of bLf. Altogether, our data improve the comprehension of bLf stability and uptake, adding knowledge to its potential use as a biopharmaceutical.