Table 2. Sequence and structural homology of essential genes and their high copy suppressors.

Essential gene	HCS	Amino acid alignment e-value	Structural homology p-value (−ln)
dapA*	nanA	4.7e−22	31.26
fldA*	fldB	1.7e−33	22.49
pyrH*	cmk	0.26	1.23
spoT*	mutT	0.14	2.28
degS	degP	2.7e−47	20.99
degS	yciR	0.11	2.59
ftsK	yhbJ	0.58	1.59
lolA	dpiA	0.85	0.91
nrdA	ftnA	0.071	0.85
nrdB	ftnA	0.065	7.64
pssA	ispU	0.95	2.48
ygjD	rho	0.01	2.30

The Protein Information Resource (http://pir.georgetown.edu/pirwww/search/pairwise.shtml) was used to generate Smith-Waterman amino acid alignments and the corresponding e-values; lower e-values imply higher homology between sequences [28]. MAMMOTH (Matching Molecular Models from Theory) [29] was used to generate pairwise structural alignments; a value above 4.5 (p = 0.01) indicates significant structural homology [29]; if no structure was available, a structure model from http://modbase.compbio.ucsf.edu/modbase-cgi/index.cgi was used. Essential genes that could be knocked out in the presence of their HCS are indicated with an asterisk.