Biochem. J. (2000) 352
(739–745) (Printed in Great Britain)
Susceptibility of mitogen-activated protein kinase kinase family members to proteolysis by anthrax lethal factor
Gaetano VITALE*1, Lorenzo BERNARDI*, Giorgio NAPOLITANI*, Michèle MOCK† and Cesare MONTECUCCO*
*Centro CNR Biomembrane and Dipartimento di Scienze Biomediche, Università di Padova, Via Trieste 75, 35121 Padova, Italy, and †Unité Toxines et Pathogénie Bactérienne, (URA 1858, CNRS), Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
The lethal factor (LF) produced by toxigenic strains of Bacillus anthracis is a Zn2+-endopeptidase that cleaves the mitogen-activated protein kinase kinases (MAPKKs) MEK1, MEK2 and MKK3. Using genetic and biochemical approaches, we have extended the study of LF proteolytic specificity to all known MAPKK family members and found that LF also cleaves MKK4, MKK6 and MKK7, but not MEK5. The peptide bonds hydrolysed by LF within all MAPKKs were identified. Cleavage invariably occurs within the N-terminal proline-rich region preceding the kinase domain, thus disrupting a sequence involved in directing specific protein–protein interactions necessary for the assembly of signalling complexes. Alignment of the sequences flanking the site of cleavage reveals the occurrence of some consensus motifs: position P2 and P1´ are occupied by hydrophobic residues and at least one basic residue is present between P4 and P7. The implications of these findings for the biochemical activity and functional specificity of LF are discussed.
Key words: bacterial toxin, metallopeptidase, signal transduction.
Abbreviations used: GST, glutathione S-transferase; LF, lethal factor; LeTx, lethal toxin; MAPK, mitogen-activated protein kinase; MAPKK, MAPK kinase; PA, protective antigen.
1To whom correspondence should be addressed. Present address: University of Udine, Department of Biomedical Sciences and Technologies, P.le Kolbe 4, 33100 Udine, Italy (e-mail gvitale@makek.dstb.uniud.it).
Received 27 July 2000/22 September 2000; accepted 10 October 2000
The Biochemical Society, London ©
2000
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