Influence of Physico-Chemical Factors on the Oligomerization and Biological Activity of Bacteriocin AS-48 |
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Authors: | Hikmate Abriouel Eva Valdivia Antonio Gálvez Mercedes Maqueda |
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Institution: | (1) Dpto. Microbiología, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, E-18071-Granada, Spain, ES;(2) Area de Microbiología, Facultad de Ciencias Experimentales, Universidad de Jaén, E-23071 Jaén, Spain, ES |
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Abstract: | Bacteriocin AS-48 forms a mixture of monomers and oligomers in aqueous solutions. Such oligomers can be clearly differentiated
by SDS-PAGE after formaldehyde crosslinking, and we have verified that these associates are stable to acid treatment after
fixation. In addition, they show antimicrobial activity and are recognized by anti-AS-48 antibodies. AS-48 oligomers can be
dissociated by the detergents SDS and Triton X-100. The degree of oligomerization of AS-48 depends on the pH of the solution
and the protein concentration. At pH below 5, AS-48 is in the monomeric state at protein concentrations below 0.55.mg ml−1, but it also forms dimers above this protein concentration. This bacteriocin forms oligomers at pH values above 5, in agreement
with the observation that it is also more hydrophobic at neutral pH. AS-48 is stable to mild heat treatments irrespectively
of pH. At 120°C it is more heat resistant under acidic conditions, but it inactivates at neutral pH. Activity of AS-48 against
E. faecalis is highest at neutral pH, but it is highest at pH 4 for E. coli. The influence of pH on bacteriocin activity could be owing to changes in the conformation/oligomerization of the bacteriocin
peptide as well as to changes in the surface charge of the target bacteria.
Received: 3 July 2000\t/\tAccepted: 11 August 2000 |
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