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* AP endonucleases family 2 signatures *
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DNA damaging agents such as the antitumor drugs bleomycin and neocarzinostatin
or those  that  generate  oxygen radicals produce a variety of lesions in DNA.
Amongst these  is  base-loss  which  forms apurinic/apyrimidinic (AP) sites or
strand breaks with atypical 3'termini. DNA repair at the AP sites is initiated
by specific   endonuclease  cleavage  of  the  phosphodiester  backbone.  Such
endonucleases are  also generally capable of removing blocking groups from the
3'terminus of DNA strand breaks.

AP endonucleases  can be classified into two families on the basis of sequence
similarity. What we call family 2 groups the enzymes listed below [1].

 - Escherichia coli endonuclease IV (EC 3.1.21.2) (gene nfo).
 - Mycobacterium leprae probable endonuclease (gene end) [2].
 - Yeast apurinic endonuclase APN1.

APN1 and nfo have been shown [3] to be transition metalloproteins that seem to
bind zinc and manganese.

We developed three signature patterns for this family of enzymes. The patterns
are based  on  regions that contain  conserved  cysteines and histidines which
could be involved in binding metal ions.

-Consensus pattern: H-x(2)-Y-[LIVMF]-I-N-[LIVM]-[AG]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: G-[LIVMF]-C-[LIVM]-D-T-C-H
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: [LIVM]-H-x-N-D-[SA]-K-x(3)-G-[SA]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Last update: June 1994 / Patterns and text revised.

[ 1] Popoff S.C., Spira A.I., Johnson A.W., Demple B.
     Proc. Natl. Acad. Sci. U.S.A. 87:4193-4197(1990).
[ 2] Honore N.T., Bergh S., Chanteau S., Doucet-Populaire F., Eiglmeier K.,
     Garnier T., Georges C., Launois P., Limpaiboon T., Newton S., Niang K.,
     del Portillo P., Ramesh G.R., Reddi P., Ridel P.R., Sittisombut N.,
     Wu-Hunter S., Cole S.T.
     Mol. Microbiol. 7:207-214(1993).
[ 3] Levin J.D., Shapiro R., Demple B.
     J. Biol. Chem. 266:22893-22898(1991).