Four different mutations in codon 28 of alpha spectrin are associated with structurally and functionally abnormal spectrin alpha I/74 in hereditary elliptocytosis.

Abstract

IntroductionHereditary elliptocytosis (HE) Sp aoP4 is a disorder associated with defective spectrin (Sp) heterodimer self-association and an abnormal tryptic cleavage of the 80-kD aI domain of Sp resulting in increased amounts of a 74-kD peptide. The molecular basis of this disorder is heterogeneous and mutations in codons 28, 46, 48, and 49 (codons 22, 40, 42, and 43 in the previous nomenclature which did not include the six NH2-terminal amino acids) have been reported. In this study we present data on seven unrelated HE Sp all4 kindred from diverse racial backgrounds in whom we identified four different mutations all occurring in exon 2 of a Sp at codon 28. Utilizing the polymerase chain reaction we established a CGT 7CTT; Arg --Leu 28 mutation in one kindred of Arab/Druze origin. In two unrelated white kindred of English/European origin the substitu-

Interactions within the Coiled-coil Domain of RetGC-1 Guanylyl Cyclase Are Optimized for Regulation Rather than for High Affinity

“…Mutations that disrupt the coiled-coil domains of structural proteins, such as keratin and spectrin, have also been linked to autosomal dominant human diseases (55,56). Most substitutions in keratin that cause the skin disorder, epidermolytic hyperkeratosis, occur at the beginning or end of a coiled-coil rod domain (57).…”

Nuclear magnetic resonance studies of mutations at the tetramerization region of human alpha spectrin

“…However, the relative affinities among these peptides are clearly defined, with the native Arg28/Arg45 peptide having the highest affinity, Arg45Ser and Arg28Ser having the lowest affinities (and being statistically equivalent to each other), and Arg45Thr having an intermediate affinity, between the Arg45Ser and Arg28Ser substituted peptides and the native Arg28/Arg45 peptide. It is interesting to note that patients with the Arg28Ser spectrin mutation suffer severe symptoms 10,17 and some patients with the Arg45Ser spectrin mutation also suffer severe symptoms, 10,16 whereas patients with the Arg45Thr mutation show only mild symptoms. 11 Therefore, our ␣␤ model-peptide association affinities appear to be correlated with the severity of disease symptoms.…”

“…It is crucial to determine whether the impaired ␣␤ association in Arg28Ser, Arg45Ser, and Arg45Thr associated with a single amino acid replacement is due to a disruption of helix 3 (Helix CЈ) conformation, as has widely been suggested, 10,11,16,17,26 or is simply a disruption of molecular interactions involved in the ␣␤ molecular recognition and association, without significant change in Helix CЈ conformation in the ␣-peptide.…”

“…10,16 Mutations at position 28 from Arg to His, Leu, Ser, or Cys all induce severe clinical symptoms. 10,17 All of these mutations apparently reduce ␣␤ tetramerization. 10 In this study, we focus on the effects of specific amino acid replacements on ␣-and ␤-spectrin association at the tetramerization site.…”

Laboratory method to study mutational effects on human erythrocyte spectrin tetramerization

“…Thus mutations along this hydrophobic face, for example at positions 24 ("d" position), 35 ("a" position), and 38 ("d" position), would affect ␣␤ complex formation. Position Genotype mutation Codon 16 27 35 9 49 53 53 24 38 Phenotype mutation K16M R27G Y35N No change L49H Y53N Y53C I24N F38S 28, which is at the "a" position, has been identified, clinically, as a "hot spot" for mutations [22]. Position 27 is in the "g" position, and many coiled-coil helix associations involve electrostatic interactions of residues at "e" and "g" positions [21].…”