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

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.