Self-aggregation of human apolipoprotein AI. Studies with pyrenyl-maleimide labeled cysteine mutants

TARRAGA, WILSON; GONZALEZ, MARINA; FALOMIR LOCKHART, LISANDRO J.; TOLEDO, JUAN; GARDA, HORACIO A.

Mar del Plata

Congreso; LI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2015

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The apolipoprotein A-I (apo A-I) is the major protein of high density lipoproteins (HDL), to which antiatherogenic properties are attributed for its role in the transport of cholesterol excess from peripheral tissues to the liver for catabolism and disposal.Apo A-I is composed of several amphipathic alpha-helices. In water solution, they form a bundle with poorly defined tertiary structure. Depending on the concentration, apo A-I is self-aggregated to form dimers and oligomers of different size.The aim was to obtain information on the apo A-I self-aggregation in solution, as well as its interaction with membrane, since it is important to understand the mechanisms of HDL generation. Six cysteine mutants (K107C, K133C F104C, L137C, K226C and F225C) were specifically labeled with pyrenyl maleimide in these six positions corresponding to the hydrophilic and hydrophobic faces of helices 4, 5 and 10. Fluorescence emission spectra in function of the protein concentration showed that pyrene excimer formation occurs only in the case of labeled F225C and K133C mutants, indicating the participation of helices 5 and 10 in the contact regions for oligomerization.