Family M78


Summary Holotypes Alignment Tree Genomes Structure Literature

Summary for family M78

Family type peptidaseM78.001 - ImmA peptidase (Bacillus subtilis), MEROPS Accession MER0144929 (peptidase unit: 1-169)
Content of familyFamily M78 contains metallo-endopeptidases.
History Identifier created: MEROPS 8.3 (22 December 2008)
Conjugating bacteria are able to transfer genetic elements that can, for example, confer resistance to antibiotics. These genetic elements, known as conjugative transposons, are integrated into the chromosome, but during conjugation excise themselves and then move to the recipient bacterium and re-integrate into its chromosome. Typically a conjugative tranposon enodes only the proteins required for this activity and proteins that regulate it. During exponential growth, the ICEBs1 transposon of Bacillus subtilis is inactivated by the immunity repressor protein ImmR, which is encoded by the transposon and represses the genes for excision and transfer. Cleavage of ImmR relaxes repression and allows transfer of the transposon. The protein ImmA (M78.001), also encoded by the transposon, has been shown to be essential for the cleavage of ImmR (Bose et al., 2008).
Catalytic typeMetallo
Active site residuesH75 E76 H79 E103 
Active siteProteins in this family are assumed to be zinc-dependent metallopeptidases because of the presence of a conserved HEXXH motif. A conserved Glu C-terminal to this motif might be the third zinc ligand. Mutation of His75 (to Ala) prevented cleavage of ImmR in vitro (Bose et al., 2008).
Activities and specificitiesCleavage of ImmR occurs at Phe95+Met, releasing the N-terminal DNA-binding domain (Bose et al., 2008).
Molecular structureNo tertiary structure has been solved for any member of this family. The family is included in clan MA because of the presence of the HEXXH putative zinc-binding motif, and in subclan MA(E) because of the third zinc ligand might be Glu.
Distribution of family Bacteria details  
Archaea details  
Protozoa -  
Fungi -  
Plants -  
Animals -  
Viruses details  
Biological functionsBy cleaving the ImmR protein, the ImmA peptidase allows excision of the ICEBs1 transposon and transfer of genetic material, but it is not known what advantage this passes on to the recipient bacterium.
Statistics for family M78Sequences:2061
Identifiers with PDB entries:1
Downloadable files Sequence library (FastA format)
Sequence alignment (FastA format)
Phylogenetic tree (Newick format)
Peptidases and Homologues MEROPS ID Structure
ImmA peptidaseM78.001-
IrrE peptidase (Deinococcus sp.)M78.002Yes
family M78 non-peptidase homologuesnon-peptidase homologue-
family M78 unassigned peptidasesunassigned-