title: Apolipoprotein A-I binding to anionic vesicles and lipopolysaccharides: role for lysine residues in antimicrobial properties.
abstract: Human apolipoprotein A-I (apoA-I) is a 28kDa protein and a major component of high-density lipoproteins, mediating several essential metabolic functions related to heart disease. In the present study the potential protective role against bacterial pathogens was explored. ApoA-I suppressed bacterial growth of Escherichia coli and Klebsiella pneumoniae. The protein was able to bind lipopolysaccharides and showed a strong preference for bilayer vesicles made of phosphatidylglycerol over phosphatidylcholine. Lysine side chains of apoA-I were acetylated to evaluate the importance of electrostatic forces in the binding interaction with both membrane components. Electrophoresis properties, dot blot analysis, circular dichroism, and fluorescence spectroscopy to probe for changes in protein structure indicated that the acetylated protein displayed a strongly reduced lipopolysaccharide and phosphatidylglycerol binding. A mutant containing only the N-terminal domain of apoA-I also showed a reduced ability to interact with the membrane components, although to a lesser extent. These results indicate the potential for apoA-I to function as an antimicrobial protein and exerts this function through lysine residues.
authors: Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, CA 90840, USA.
authors: Wendy H J
authors: WH
authors: Beck
authors: Christopher P
authors: CP
authors: Adams
authors: Ivan M
authors: IM
authors: Biglang-Awa
authors: Arti B
authors: AB
authors: Patel
authors: Heather
authors: H
authors: Vincent
authors: Eric J
authors: EJ
authors: Haas-Stapleton
authors: Paul M M
authors: PM
authors: Weers
mesh_terms: D000107:Acetylation; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D016632:Apolipoprotein A-I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D002942:Circular Dichroism; D015169:Colony Count, Microbial; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D006801:Humans; D015151:Immunoblotting; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000254:growth & development; D008051:Lipid Bilayers; D008070:Lipopolysaccharides / Q000378:metabolism*; D008239:Lysine; D016297:Mutagenesis, Site-Directed; D010713:Phosphatidylcholines / Q000378:metabolism; D010715:Phosphatidylglycerols / Q000378:metabolism; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D055672:Static Electricity; D013329:Structure-Activity Relationship
chemical_list: C505693:APOA1 protein, human; D000900:Anti-Bacterial Agents; D016632:Apolipoprotein A-I; D008051:Lipid Bilayers; D008070:Lipopolysaccharides; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D011994:Recombinant Proteins; D008239:Lysine