Hemolysin from Listeria--biochemistry, genetics and function in pathogenesis

Abstract

Thiol-activated hemolysins (listeriolysins) from Listeria monocytogenes (Sv4b) and Listeria ivanovii were purified to homogeneity. The N-terminal amino acid sequences of the 58 kDa listeriolysin of L. ivanovii and of a 24 kDa protein which may represent the CAMP-factor of L. ivanovii were determined. Antibodies raised against the L. ivanovii listeriolysin and anti-streptolysin O antibodies were used in Western blot analyses to detect listeriolysin(s) in virulent and avirulent Listeria strains. It was found that all virulent strains of L. monocytogenes synthesize and secrete listeriolysin (Mr 58-59 kDa), albeit in significantly variable quantities. No protein cross-reaction with anti-listeriolysin antibodies or anti-streptolysin O-antibodies was present in the supernatant of Listeria innocua, Listeria welshimeri, Listeria grayi and Listeria murrayi strains. Furthermore, the avirulent but hemolytic Listeria seeligeri did not cross-react with these antibodies. In a L. monocytogenes (strain EGD) gene bank constructed in Escherichia coli two types of hemolytic clones were identified. The first type carried recombinant plasmids with a common 2.0 kb fragment coding for a 23 kDa protein. This hemolytic activity was not activated by DTT and the 23 kDa protein did not cross react with anti-listeriolysin or anti-streptolysin antibodies. The other type of hemolytic clones was detected by using anti-streptolysin O antibodies to screen the gene bank. Some of these clones synthesized a protein of 61 kDa which cross reacted with anti-streptolysin O (or anti-listeriolysin) antibodies. By transposon Tn916 mutagenesis of L. monocytogenes two types of nonhemolytic mutants were obtained. Type I produced no extracellular protein that cross reacted with anti-listeriolysin (or anti SLO) antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)