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I think no, but I am not sure since Listeria is Gram-positive and probably has lipopolysaccharide (exception among Gram positive bacteria).

Can Listeria monocytogenes' endotoxin act like exotoxin A-B? (In which component B lets component A inside the cell and component A causes the toxicity.)

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Considering great research we did after the answer was accepted, I should add important information about the topic. The old (and accepted) answer follows in "" marks for the sake of clarity.

We found that in spite of the earlier reports, the newest ones failed to find endotoxin-like structure in the Listeria born material. Most academic discussions about the issue say there is no such thing called "listeric endotoxin", thus I gave a right answer to a "compromised" question.

I should say that question is still brilliant because it promoted great research and should be an important source for everyone looking for information about listeric "endotoxin"

Listeria endotoxin is not a protein. Thus, is lacks enzymatic activity and acts indirectly by binding to sensitive receptors on macrophages. Thus, it can not cause lysis itself.

Considering AB-exotoxins, A-subunit is a protein that has enzymatic activity (responsible for toxin action) and subunit B has no enzymatic activity (protein responsible for binding to receptors).

Thus, the answer to your brilliant question is NO, Listeria endotoxin cannot act as AB-exotoxin being nonprotein and non enzymatic substance.

Also, don't be confused with Listeriolysin O, which is listeria's eXotoxin protein which is pore-creating protein.

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Just to add some important relevant information to the answer from @Ilan.

There is no evidence for the presence of endotoxin/lipopolysaccharide in Listeria.

There was an early report of the presence of LPS (Wexler & Oppenheim, 1979) but this was contradicted by a later study (Maitra et al., 1986). The endotoxin activity of Gram negative bacteria is strongly associated with the lipid A moiety of the LPS. Lipid A is synthesised from N-acetylglucosamine in a three step pathway encoded by the genes lpxA, lpxC and lpxD. I obtained the sequences for the corresponding E. coli gene products and conducted BLAST searches against the Listeria monocytogenes genome with these results:

lpxA - best hit E=0.11

lpxC - no significant hit

lpxC - best hit E=1e-04

the last hit is to a 2,3,4,5-tetrahydropyridine-2,6-carboxylate N-succinyltransferase whereas the E. coli gene encodes a UDP-3-O-(3-hydroxymyristoyl)glucosamine N-acyltransferase. The similarity in the sequences seems to be because they are both members of a large superfamily of acyltransferases.

I conclude that Listeria monocytogenes does not not synthesise lipid A and therefore has no LPS, and no endotoxin.

Wexler, H., and J. D. Oppenheim. 1979. Isolation, characterization, and biological properties of an endotoxin-like material from the gram-positive organism Listeria monocytogenes. Infect.Immun. 23:845-857.

Maitra, SK et al. (1986) Establishment of beta-hydroxy fatty acids as chemical marker molecules for bacterial endotoxin by gas chromatography-mass spectrometry. Appl. Env. Mic. 52: 510-514

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  • $\begingroup$ Thank you for the addition! I corrected Ilan's answer accordingly. $\endgroup$
    – Léo Léopold Hertz 준영
    Mar 2, 2014 at 13:37
  • $\begingroup$ I"m away from sources now, but I met sources said endotoxin exists $\endgroup$
    – Ilan
    Mar 2, 2014 at 13:46
  • $\begingroup$ @ilan I tried pretty hard to find any references, so I'll be interested to see what you found. $\endgroup$
    – Alan Boyd
    Mar 2, 2014 at 13:57
  • $\begingroup$ No problem, will look for the sources later. $\endgroup$
    – Ilan
    Mar 2, 2014 at 14:43
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    $\begingroup$ @AlanBoyd I tend to agree that Listeria does not produce endotoxin at all. However, multiple sites and even USMLE examination board state it does produce endotoxin. I found older articles than you did, so at this moment I upvote your answer as important one. Although my answer was right, but the question itself was probably biased and compromised. $\endgroup$
    – Ilan
    Mar 2, 2014 at 21:05

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