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C = distance from the nearest active site, in residues.
c = successively: active site residues, amino acids 1 residue away from the nearest active
site residue, 2 residues away, etc.
D = 28050 residues in the dataset of 94 proteins
H = 378 hinge residues in the dataset
dc = residues of class c in the dataset
hc = residues of class c in hinges.
The results are shown in Figure 2.2 and Table 2.2. At short distances from the active
sites, hinge residues were overrepresented. The active site residues and residues as much
as four residues away from the nearest active site were significantly overrepresented in
hinges.
Are hinges segregated by secondary structure?
It is generally accepted that hinges tend to avoid secondary structure. However this
belief has, to our knowledge, never been tested on a quantitative basis, and indeed
numerous counterexamples can be found. For instance, the hinge in calmodulin and
troponin C[40, 49] occurs in an α-helix, and in glutamine binding protein it occurs in two
parallel beta strands[40]. Thus we do not know which particular types of secondary
structure are avoided or preferred, or to what degree. To obtain this information, we
tabulated the number of hinge residues occurring in the various types of secondary
structural elements, and compared this with the distribution of all residues, proceeding as
follows.
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