Abstract
Lecithin:cholesterol-acyl transferase (LCAT) plays a major role in cholesterol metabolism as it is the only extracellular enzyme able to esterify cholesterol. LCAT activity is required for lipoprotein remodeling and, most specifically, for the growth and maturation of HDLs. In fact, genetic alterations affecting LCAT functionality may cause a severe reduction in plasma levels of HDL-cholesterol with important clinical consequences. Although several hypotheses were formulated, the exact molecular recognition mechanism between LCAT and HDLs is still unknown. We employed a combination of structural bioinformatics procedures to deepen the insights into the HDL-LCAT interplay that promotes LCAT activation and cholesterol esterification. We have generated a data-driven model of reconstituted HDL (rHDL) and studied the dynamics of an assembled rHDL::LCAT supramolecular complex, pinpointing the conformational changes originating from the interaction between LCAT and apolipoprotein A-I (apoA-I) that are necessary for LCAT activation. Specifically, we propose a mechanism in which the anchoring of LCAT lid to apoA-I helices allows the formation of a hydrophobic hood that expands the LCAT active site and shields it from the solvent, allowing the enzyme to process large hydrophobic substrates.
Highlights
Lecithin:cholesterol-acyl transferase (LCAT) is a 65 kDa plasmatic protein of the α/β-hydrolase family synthesized mainly in the liver and in lower amounts in the brain, testes, and kidneys
The solar flare model proposed by Wu et al [13], which identified, via hydrogen-deuterium exchange experiments, solventexposed protruding bulges in apolipoprotein A-I (apoA-I) chains that were proposed to activate LCAT; the belt buckle model, from Bhat et al [14], where cross-linking/MS data were collected on 145 POPC reconstituted HDL particles, showing that the N and C termini folded back onto apoA-I helices; the looped belt model, by Martin et al [15], generated by performing electron paramagnetic resonance and Förster resonance energy transfer experiments on 100 POPC rHDLs, suggesting the presence of a central loop region comprised by residues 133–146
Another model was proposed by Wu et al [16] in accordance with Förster resonance energy transfer, ESR, and cross-linking/ MS data obtained by others; this model displayed apoAI helices spiraling around a 100 POPC cylindrical core as a double superhelix; the reliability of this model was challenged by Jones et al [17] who tested the thermodynamic and kinetic stability of the double superhelix via extensive coarse-grained and simulatedannealing molecular dynamics (MD) simulations
Summary
Lecithin:cholesterol-acyl transferase (LCAT) is a 65 kDa plasmatic protein of the α/β-hydrolase family synthesized mainly in the liver and in lower amounts in the brain, testes, and kidneys. The solar flare model proposed by Wu et al [13], which identified, via hydrogen-deuterium exchange experiments, solventexposed protruding bulges in apoA-I chains (corresponding to residues 159–180) that were proposed to activate LCAT; the belt buckle model, from Bhat et al [14], where cross-linking/MS data were collected on 145 POPC reconstituted HDL (rHDL) particles, showing that the N and C termini folded back onto apoA-I helices; the looped belt model, by Martin et al [15], generated by performing electron paramagnetic resonance and Förster resonance energy transfer experiments on 100 POPC rHDLs, suggesting the presence of a central loop region comprised by residues 133–146. We employed a combination of computational approaches to model a rHDL and analyze the structure-function relationships underlying the LCAT reaction mechanism and activation mediated by apoA-I
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
