title: Sequence-specific apolipoprotein A-I effects on lecithin:cholesterol acyltransferase activity.
abstract: Existing kinetic data of cholesteryl ester formation by lecithin:cholesterol acyltransferase in discoidal high-density lipoproteins with 34 mutations of apoA-I that involved all putative helices were grouped by cluster analysis into four noncoincident regions with mutations both without any functional impairment and with profound isolated (V- and K-mutations) or common (VK-mutations) effect on V(max)(app) and K(m)(app). Data were analyzed with a new kinetic model of LCAT activity at interface that exploits the efficiency of LCAT binding to the particle, particle dimensions, and surface concentrations of phosphatidylcholine and cholesterol. V-mutations with major location in the central part and C-domain affected the second-order rate constant of cholesteryl ester formation at the solvolysis of acyl-enzyme intermediate by cholesterol as nucleophile. The central region in apoA-I sequence is suggested to influence the proper positioning of cholesterol molecule toward LCAT active center with major contribution of arginine residue(s). K-mutations with major location in N-domain may affect binding and stability of enzyme-phosphatidylcholine complex. VK-mutations may possess mixed effects; the independent binding measurement may segregate individual steps.
authors.affiliation: National Research Centre for Preventive Medicine, Moscow, Russia. dergunov@img.ras.ru
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Dergunov
mesh_terms: D000465:Algorithms; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000235:genetics; D020134:Catalytic Domain; D002784:Cholesterol / Q000737:chemistry; D016000:Cluster Analysis; D006801:Humans; D007700:Kinetics; D008956:Models, Chemical; D020125:Mutation, Missense; D010316:Particle Size; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary
chemical_list: D016632:Apolipoprotein A-I; D010713:Phosphatidylcholines; D002784:Cholesterol; D007862:Phosphatidylcholine-Sterol O-Acyltransferase