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A novel silent posttranslational mechanism converts methionine to aspartate in hemoglobin Bristol (beta 67[E11] Val-Met->Asp).

Abstract
The first reported case of congenital Heinz body hemolytic anemia was subsequently shown to be caused by an unstable hemoglobin, Hb Bristol [beta 67(E11) Val-Asp]. This has become one of the classic models of an unstable hemoglobin, the hydrophilic aspartate disrupting the hydrophobic heme pocket. We have restudied this original case, who remains clinically well after nearly 50 years of severe hemolysis with a hemoglobin level of about 7 g/dL and two unrelated Japanese cases. Surprisingly, all three cases show the same DNA changes, predicting a valine to methionine change at beta 67, rather than the expected aspartate. Further analysis with electrospray ionization mass spectrometry and globin chain biosynthesis strongly suggests that this anomaly is because of a novel posttranslational mechanism, with slow conversion of the translated methionine into an aspartate residue. The proximity of the heme and oxygen may be important in facilitating the reaction. These findings show the importance of complete characterization of variant hemoglobins using protein, DNA, and biosynthetic analyses.
AuthorsD C Rees, J Rochette, C Schofield, B Green, M Morris, N E Parker, H Sasaki, A Tanaka, Y Ohba, J B Clegg
JournalBlood (Blood) Vol. 88 Issue 1 Pg. 341-8 (Jul 01 1996) ISSN: 0006-4971 [Print] United States
PMID8704193 (Publication Type: Case Reports, Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Hemoglobins, Abnormal
  • Aspartic Acid
  • Globins
  • hemoglobin Bristol
  • Methionine
  • Valine
Topics
  • Adolescent
  • Amino Acid Sequence
  • Anemia, Hemolytic (blood, genetics)
  • Aspartic Acid (biosynthesis)
  • Base Sequence
  • DNA Mutational Analysis
  • Globins (genetics, metabolism)
  • Heinz Bodies
  • Hemoglobins, Abnormal (genetics, metabolism)
  • Humans
  • Male
  • Mass Spectrometry
  • Methionine (metabolism)
  • Middle Aged
  • Molecular Sequence Data
  • Protein Processing, Post-Translational
  • Valine

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