Table 1.

RecU_Mge mutants and their activities

Mutant	HJ-binding activityb	HJ cleavage activityc	Mutant groupd
Point mutantsa
N5A	+++	+++	A
G7A	+++	+	B
M8A	+++	+++	A
L10A	+	+	B
E11A	+++	−	C
N15A	++	++	A
K31A	++	−	C
V46A	+++	+	B
S54A	++	++	A
D57A	+++	−	C
Y58A	+	−	C
G60A	−	−	D
Y62A	++	+++	A
G64A	++	+++	A
Y66A	+	−	C
D68A	+++	−	C
F69A	−	−	D
E70A	+++	−	C
K72A	+	−	C
T74A	+	−	C
K76A	+	−	C
F79A	−	−	D
H87A	+++	+	B
Q88A	+++	−	C
H91A	−	−	D
L92A	++	−	C
G100A	−	−	D
F103A	−	−	D
F108A	−	−	D
D112A	+++	+++	A
L122A	+++	++	A
Deletion mutantse
N terminal
NΔ2	+++	+++
NΔ3	+++	+++
NΔ5	++	+
NΔ8	++	−
NΔ11	−	−
NΔ18	−	−
NΔ31	−	−
NΔ54	−	−
NΔ79	−	−
C terminal
CΔ3	++	+
CΔ9	−	−
CΔ13	−	−
CΔ19	−
CΔ23	−	−
CΔ35	−	−
CΔ112	−	−

^aThe names of the point mutants indicate the amino acid that was changed, using the one-letter amino acid code, followed by its position within the RecU_Mge protein and an A, which indicates the alanine into which the original amino acid was changed.

^bHJ-binding reactions were performed as described in Materials and Methods, using 400 nM protein. The listed activities represent the percentage of activity as opposed to that of wild-type (wt) RecU_Mge. These activities are defined as follows: −, <5%; +, 5% to 20%; ++, 20% to 70%; +++, >70%.

^cHJ cleavage reactions were performed as described in Materials and Methods, using 400 nM protein. The percent cleavage (as opposed to wt protein) refers to cleavage at the specific site within substrate HJ 1.1, resulting in a 23-nucleotide product (26). The activities are defined as follows: −, <5%; +, 5% to 20%; ++, 20% to 70%; +++, >70%.

^dThe classification of mutant proteins in groups A to D is explained in the text.

^eThe names of the deletion mutants contain either N, for N terminus, or C, for C terminus, followed by Δ and the number of amino acid residues that were deleted from either of the two RecU_Mge termini.