Biology Reference
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Potential Conformers ( PC )
(10 n )
Conformers
Functional Conformers ( FC )
(~20% of AC?)
Actual Conformers ( AC )
(~2 n' ; n' << < n )
Non-Functional Conformers ( NC )
(~ 80% of AC ?)
Fig. 11.29 The postulated hierarchical organization of the conformers of a protein. The number of
PC is estimated to be 2 n , where n is the number of the amino acid residues, and the number of AC is
thought to be far less than that of PC, i.e., AC <<< PC, and those of FC and NC are probably
comparable: FC ~ NC. The number n appears in both Figs. 11.23 and 11.28 , but Fig. 11.23 deals
with the number of all possible linear sequences of n nucleotides (i.e., configurations) whereas
Fig. 11.28 is concerned with the number of all possible three-dimensional arrangements of a given
linear sequence of n amino acid residues (i.e., conformations or conformers). The number of
potential n-nucleotide sequences is probably smaller than the number of the conformers theoreti-
cally possible for a protein with n amino acid residues, because the former is 4 n whereas the latter is
x n where x is the number of possible orientations that an amino acid residue can assume as it is being
added to the growing polypeptide chain during protein synthesis, x being most likely larger than 4
are denoted as C i in Fig. 11.28 , where i runs from 1 to n, the total number of
conformers belonging to a molecule of COx which can be astronomically large.
Since COx has 504 amino acid residues, n could be as large as 2 504 or about
10 152 , assuming that each amino acid residue added during protein synthesis on
the ribosome leads to at least two new conformational states for the resulting
polypeptide. Of these theoretically predicted large number of conformers of
COx, it is expected that only a small number, n 0 , would be selected by evolution
to be realized in COx under the intracellular environmental conditions: i.e.,
n 0 <<<
n. It is difficult to estimate the precise magnitude of n 0 . Whatever the
actual size of n 0 will turn out to be, it is probably reasonable to assume that most,
if not all, of these n 0 conformers serve some biological functions in order for
them to be evolutionarily conserved. Thus n 0 conformers may be divided into
two classes - functional and nonfunctional under a given environmental condi-
tion. The n conformers that are theoretically predictable, whether realized or not
in cells, represents a third class to be referred to as potential conformers in
contrast to actual conformers which divide into functional and nonfunctional
ones. Thus, conformers can be classified as shown in Fig. 11.29 .
As discussed in Sect. 11.3.2 , the three terms molecules, conformers, and
conformons are distinct and their mutual relations may be simply summarized as
follows:
A molecule is a set of confomers; a conformer is a set of conformons. (11.40)
A conformer of an enzyme may contain one or more conformons belonging to
two different classes: (a) the conformons (i.e., conformational kinks) introduced
into an enzyme during its biosynthesis on ribosomes and (b) the conformons
 
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