Biology Reference
In-Depth Information
structural reorganization of the protein backbone in one part of the mole-
cule causes structural and energy changes in the whole molecule. Each
step of the opening of the model causes an increase in the energy of the
whole molecule (the total energy of the P0_Ex_B model is
−
3993.887
kJ/mol; for the P0_Ex_C model it is
−
3763.946 kJ/mol; and for P0_Ex_D
it is 3207.501 kJ/mol).
Medical Implications — Autoimmune Epitopes
of Myelin P0 Protein
The regions
52
His
…
76
Pro and
180
Ala
…
199
Ser of the P0 protein (Figs. 6(B)
and 6(C) and 14(A) and 14(B)) are known to be autoimmune epitopes
(Zou
et al
., 2000; Westall, 2006; Sedzik, 2008). The study of the 3D
structure of the model of the P0 protein allows one to estimate more
potential autoimmune peptides. Here, two types of epitopes have been
selected: short epitopes consisting of a single secondary structure
domain, i.e. one strand of
-sheet (Table 2) and long epitopes contain-
ing two secondary structure domains, i.e. two anti-parallel strands of
β
β
-sheet (Table 3).
Two structural criteria of epitope estimation have been taken into
account. First, each epitope has to be located on the external surface of the
protein in order to be easily accessible for the receptor. Second, two struc-
tural domains of “long epitopes” should be neighbors (for example, two
parallel or antiparallel strands). In accordance with the above criteria, six
short and two long peptides are favored (Tables 2 and 3). Among the short
peptides, three are located in the P0_Ex part and three others in the P0_Int
part of the molecule (Table 2). P0_Ex contains one long epitope and the
second is in the P0_Int subunit (Table 3). All the details of each peptide
are summarized in Tables 2 and 3.
Summary and Discussion
The P0 protein is an abundant protein of peripheral myelin. A very
hydrophobic membrane protein, it is not soluble in water and, therefore,
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