SP ALPHA-I-65 - A NEW VARIANT OF THE ALPHA-SUBUNIT OF SPECTRIN IN HEREDITARY ELLIPTOCYTOSIS

  • 1 January 1985
    • journal article
    • research article
    • Vol. 66  (3) , 706-709
Abstract
Two molecular defects involving the spectrin heterodimer (SpD) contact site of the .alpha. chain (the .alpha.I domain) were previously identified using limited tryptic digestion followed by two-dimensional isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both are characterized by atypical peptide maps which reveal a marked decrease of the 80,000-dalton .alpha.I domain and a formation of new major peptides of either 74,000 (Sp .alpha.I/74) or 46,000 (Sp .alpha.I/46) daltons. We now report a third variant of the spectrin .alpha. chain, designated Sp .alpha.I/65, in three unrelated black families. In all three probands, the percentage of SpD in the low ionic strength (0.degree. C) membrane extracts was increased to 19% to 32%. One- and two-dimensional electrophoretic separations of limited tryptic digests of spectrin from all three probands revealed a decrease of the .alpha.I domain of spectrin and the concomitant appearance of peptides at 65,000 daltons and isoelectric points ranging from 5.2 to 5.3. The abnormal 65,000-dalton peptides could be stained with an antiserum which had been raised against the .alpha.I domain, indicating that it was derived from the .alpha.I domain.