Table 3.

Structurally related proteins that harbor the ccc substructure

Protein	PDB code	Class notation	CATH topology	DALI/FSSP fold	EC code
TnsA endonuclease	1f1z	H1-S*	3.40.1350	263	N/A
lambda exonuclease	1avq	H1-S-down	3.90.320	263	3.1.11.3
VSR endonuclease	1vsr	H1-S-H2-up	3.40.960	263	3.1.-.-
T7 endonuclease I	1fzr	H1′-S1′- S2-S3-S4-S5-H2-up	3.40.91	263	3.1.21.2
Archaeal HJC hydrolase	1gef	H1-S-H2-down	3.40.1350	263	N/A
XPF/RAD1/MUS81 nuclease	1j23	S1-H1-S2-S3-S4-S5-H2-up	3.40.50	263	N/A
HJC hydrolase	1hh1	H1-S-H2-down	3.40.1350	263	N/A
RecB endonuclease	1w36	H1-H2-S-up	1.10.3170	N/A	3.1.11.5
structural genomics	1xmx	H1-S-H2-up	N/A	N/A	N/A
structural genomics	1y88	H1-S-H2-up	3.40.91	N/A	N/A
structural genomics	1wdj	H1-S-down	3.90.1570	N/A	N/A

The columns are ordered as follows: Protein column lists the names of the proteins; PDB code column lists the pdb files of structurally related proteins that share the ccc substructure; Class notation describes the sequential order of the elements and the direction of the S5 strand with respect to the S1 strand. The prime is used to indicate that the secondary structure element belongs to a different monomer. Only four strands from the β-sheet in TnsA endonuclease; CATH topology classification (18) DALI/FSSP fold classification (32); EC code, Enzyme Classification code obtained from http://www.ebi.ac.uk/thornton-srv/databases/enzymes/. Some enzymes are not available (N/A) in the database, but all of them can be assigned to EC code 3.1.-.-, hydrolases acting on ester bonds.