Simulative and experimental investigation on the cleavage site that generates the soluble human LOX-1

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-I) is a scavenger receptor that mediates the recognition, the binding and internalization of ox-LDL A truncated soluble form of LOX-I (sLOX-1) has been identified that, at elevated levels, has been associated to acute coronary syndrome. Human 5LOX-1 is the extracellular part of membrane LOX-1 which is cleaved in the NECK domain with a mechanism that has not yet been identified. Purification of human sLOX-1 has been carried out to experimentally identify the cleavage site region within the NECK domain. Molecular modelling and classical molecular dynamics simulation techniques have been used to characterize the structural and dynamical properties of the LOX-1 NECK domain in the presence and absence of the CTLD recognition region, taking into account the obtained proteolysis results. The simulative data indicate that the NECK domain is stabilized by the coiled-coil heptad repeat motif along the simulations, shows a definite flexibility pattern and is characterized by specific electrostatic potentials. The detection of a mobile inter-helix space suggests an explanation for the in vivo susceptibility of the NECK domain to the proteolytic cleavage, validating the assumption that the NECK domain sequence is composed of a coiled-coil motif destabilized in specific regions of functional significance. (C) 2013 Elsevier Inc. All rights reserved.