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A folding variant of α‐lactalbumin with bactericidal activity against Streptococcus pneumoniae
Author(s) -
Håkansson Anders,
Svensson Malin,
Mossberg AnnKristin,
Sabharwal Hemant,
Linse Sara,
Lazou Irene,
Lönnerdal Bo,
Svanborg Catharina
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01728.x
Subject(s) - lactalbumin , biology , biochemistry , chromatography , casein , antibacterial activity , bacteria , antimicrobial , molecular mass , microbiology and biotechnology , chemistry , genetics , enzyme
This study describes an α‐lactalbumin folding variant from human milk with bactericidal activity against antibiotic‐resistant and ‐susceptible strains of Streptococcus pneumoniae . The active complex precipitated with the casein fraction at pH 4.6 and was purified from casein by a combination of anion exchange and gel chromatography. Unlike other casein components, the active complex was retained on the ion‐exchange matrix and eluted only with high salt. The eluted fraction showed N‐terminal and mass spectrometric identity with human milk α‐lactalbumin, but native α‐lactalbumin had no bactericidal effect. Spectroscopic analysis demonstrated that the active form of the molecule was in a different folding state, with secondary structure identical to α‐lactalbumin from human milk whey, but fluctuating tertiary structure. Native α‐lactalbumin could be converted to the active bactericidal form by ion‐exchange chromatography in the presence of a cofactor from human milk casein, characterized as a C18:1 fatty acid. Analysis of the antibacterial spectrum showed selectivity for streptococci; Gram‐negative and other Gram‐positive bacteria were resistant. The folding variant of α‐lactalbumin is a new example of naturally occurring molecules with antimicrobial activity.