Spectrin self-association site: characterization and study of beta-spectrin mutations associated with hereditary elliptocytosis.
Most of hereditary elliptocytosis (HE) cases are related to a spectrin dimer (SpD) self-association defect. The severity of haemolysis is correlated with the extent of the SpD self-association defect, which itself depends on the location of the mutation regarding the tetramerization site. This site is presumed to involve the first C helix of the alpha chain and the last two helices, A and B, of the beta chain to reconstitute a triple helical structure (A, B and C), as observed along spectrin. Using recombinant peptides, we demonstrated that the first C helix of the alpha chain and the last two helices of the beta chain alone are not sufficient to establish interactions, which only occurred when a complete triple-helical repeat was added to each partner. One adjacent repeat is necessary to stabilize the conformation of both N- and C-terminal structures directly involved in the interaction site and is sufficient to generate a binding affinity similar to that observed in the native molecule. Producing peptides carrying a betaHE mutation, we reproduced the tetramerization defect as observed in patients. Therefore, the betaW2024R and betaW2061R mutations, which replace the invariant tryptophan and a residue located in the hydrophobic core, respectively, affect alpha-beta interactions considerably. In contrast, the betaA2013V mutation, which modifies a residue located outside any presumed interacting regions, has a minor effect on the interaction.
Nicolas
G
G
INSERM U409, Faculté de Médecine Bichat, 75870 Paris cedex 18, France.
Pedroni
S
S
Fournier
C
C
Gautero
H
H
Craescu
C
C
Dhermy
D
D
Lecomte
M C
MC
D001665:Binding Sites / Q000235:genetics*; D002942:Circular Dichroism; D019281:Dimerization; D004612:Elliptocytosis, Hereditary / Q000235:genetics*; D004912:Erythrocytes / Q000737:chemistry; D006801:Humans; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000378:metabolism; D013049:Spectrin / Q000235:genetics / Q000378:metabolism*
D010446:Peptide Fragments; D011994:Recombinant Proteins; D013049:Spectrin