Table 2 Variation within functional categories based on sequence and structure. Which functional categories show the most variation in fold usage between organisms? The first column lists 17 TIGR cellular function categories, and an additional category composed of all proteins in each proteome. The "fold-based variation" column is based on a calculation of the coefficient of variation in the number of structurally characterized domains in each functional role in each of the first 7 SCOP classes (all-α, all-β, α/β, α+β, multi- domain, membrane, small). As described in Equation 2, the coefficient of variation is calculated separately for each of the 7 classes, and then averaged across all 7 classes to produce CV_structure. The "sequence-based variation" column gives the coefficient of variation in the number of proteins in each category (CV_sequence, Equation 1). The "fold-based rank" and "sequenced-based rank" show the ranking of functional categories based on the amount of fold-based and sequence-based variation, from lowest amount of variation to the highest. Cellular function categories are ordered in the table according to their fold-based rank.

From: Structural proteomics of minimal organisms: Conservation of protein fold usage and evolutionary implications