Role of lipopolysaccharide on the structure and function of alpha-hemolysin from Escherichia coli.
alpha-Hemolysin (HlyA) is a protein toxin (107 kDa) secreted by some pathogenic strains of E. coli. Several studies suggested the relationship between HlyA and lipopolysaccharide (LPS). We have studied experimentally the role of LPS on the stability and function of this toxin. The HlyA conformation in both, LPS-free and LPS-bound forms was investigated by tryptophan fluorescence. Studies about HlyA thermal and chemical denaturation indicated that its stability increased in the presence of LPS. On the other hand, the presence of negative and polar residues on the LPS reduced the tendency of HlyA to self-aggregation, and they may be the reservoir of calcium, cation essential for the lytic action of this toxin on red blood cells. These results suggest that HlyA and LPS are combined mainly via hydrophobic force to form an active toxin which stability is favored by the LPS.
Herlax
V
V
Instituto de Investigaciones Bioquímicas La Plata, Facultad de Ciencias Médicas, 60 y 120, 1900 La Plata, Argentina.
de Alaniz
M J T
MJ
Bakás
L
L
D029968:Escherichia coli Proteins / Q000737:chemistry*; D006460:Hemolysin Proteins / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008070:Lipopolysaccharides / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation / Q000187:drug effects; D013050:Spectrometry, Fluorescence
D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D008070:Lipopolysaccharides