Role of lipopolysaccharide on the structure and function of Ą-hemolysin from Escherichia coli

V. HERLAX; L. BAKÁS

Córdoba

Congreso; Reunión XXXVIII de SAIB (Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular); 2001

SAIB

   Alpha- hemolysin is a protein toxin (107 Kda) secreted by some pathogenics strains of E. coli. Several studies suggest the interaccion between HlyA and lipopolysaccharide (LPS). We have studied the role of LPS on the staility and function of this toxin. The HlyA conformation in both LPS-free an LPS- bound form was studies by tryptophan fluorescence and their denaturation by temperature and guanidine HCl indicating that the stability is incresed by the presence of LPS.These results are confirmed by a higher papain digestion susceptibility. On the other hand, the presence of negative and polar residues on the LPS, reduces the tendence of HlyA to self- aggregation.These results suggest that HlyA structure modification by LPS could be involve in changes of the tertiary or quaternary structure.HlyA and LPS combine by hydrophobic interaction to form an active toxin whose stability is aided by the LPS.