Table 6. Atoms close to the Glu166/OE1 in Class A β-lactamase after superimposition of the partial motifs.

1E25			2J7V			2J9O			1NZO
D	Residue	Atom	D	Residue	Atom	D	Residue	Atom	D	Residue	Atom
0	Glu166	OE1	1.6	Pro159	C	1.6	Pro159	C	1.4	LEU153	CD2
1.3	Glu166	CD	1.6	Pro159	CA	1.6	Pro159	CA	2.7	LEU153	CG
2.2	Glu166	OE2	1.8	Pro159	O	1.9	Glu158	OE1	2.8	HOH475	O
2.4	Glu166	CG	2.4	Leu158	CD1	1.9	Pro159	O
2.7	Glu166	CB	2.7	Asp160	N	2.6	Asp160	N
3	Glu166	CA	2.7	Pro159	N	2.7	Glu158	CA
3.1	HOH2076	O	2.7	Leu158	CA	2.7	Pro159	N
			2.8	Pro159	CB	2.8	Glu158	CB
			2.9	Leu158	CB	2.8	Glu158	CD
			3.1	Leu158	CG	2.9	Pro159	CB
			3.2	Leu158	C	3.1	Glu158	C
			3.4	HOH2146	O	3.3	HOH2234	O

PDBid:1E25 is the Class A Blase, PDBid:2J7V is the wildtype PBP-A, PDBid:2J9O is the L158E PBP-A mutant and PDBid:1NZO is the PBP-5 protein. It can be seen that in the Class A Blase (PDBid:1E25) and PBP-5 there are no atoms within a radius of about 3 Å of Glu166/OE1. In the mutant L158E PBP, both Pro159 and Asp160 are spatially close to Glu158, and can be seen to be obstructing access to substrate (Fig. 4). Distances are in Å, and have a cut-off till the first water molecule is encountered.