title: A model structure for the heterodimer apoA-IMilano-apoA-II supports its peculiar susceptibility to proteolysis.
abstract: In this study, we propose a structure for the heterodimer between apolipoprotein A-I(Milano) and apolipoprotein A-II (apoA-I(M)-apoA-II) in a synthetic high-density lipoprotein (HDL) containing L-alpha-palmitoyloleoyl phosphatidylcholine. We applied bioinformatics/computational tools and procedures, such as molecular docking, molecular and essential dynamics, starting from published crystal structures for apolipoprotein A-I and apolipoprotein A-II. Structural and energetic analyses onto the simulated system showed that the molecular dynamics produced a stabilized synthetic HDL. The essential dynamic analysis showed a deviation from the starting belt structure. Our structural results were validated by limited proteolysis experiments on HDL from apoA-I(M) carriers in comparison with control HDL. The high sensitivity of apoA-I(M)-apoA-II to proteases was in agreement with the high root mean-square fluctuation values and the reduction in secondary structure content from molecular dynamics data. Circular dichroism on synthetic HDL containing apoA-I(M)-apoA-II was consistent with the alpha-helix content computed on the proposed model.
authors.affiliation: Gruppo di Studio per la Proteomica e la Struttura delle Proteine, Centro E. Grossi Paoletti, Dipartimento di Scienze Farmacologiche, Università degli Studi di Milano, Milan, Italy.
authors.forename: Alessandro Guerini
authors.initials: AG
authors.lastname: Rocco
authors.forename: Luca
authors.initials: L
authors.lastname: Mollica
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Gianazza
authors.forename: Laura
authors.initials: L
authors.lastname: Calabresi
authors.forename: Guido
authors.initials: G
authors.lastname: Franceschini
authors.forename: Cesare R
authors.initials: CR
authors.lastname: Sirtori
authors.forename: Ivano
authors.initials: I
authors.lastname: Eberini
mesh_terms: D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000235:genetics; D016633:Apolipoprotein A-II / Q000737:chemistry* / Q000235:genetics; D003198:Computer Simulation; D019281:Dimerization; D006801:Humans; D006868:Hydrolysis; D008075:Lipoproteins, HDL / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D010713:Phosphatidylcholines / Q000737:chemistry; D017433:Protein Structure, Secondary
chemical_list: D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D008075:Lipoproteins, HDL; D010713:Phosphatidylcholines; C080631:apolipoprotein A-I Milano; C028694:1-palmitoyl-2-oleoylphosphatidylcholine