Delayed Removal of N-Terminal Methionine from Nascent Globin Chains in Sickle-Cell Anemia Reticulocytes
AUTOR(ES)
Suzuki, Haruo
RESUMO
Synthetic αT1 and βT1, the N-terminal tryptic peptides of α-chain and β-chain of hemoglobin, and MetαT1 and MetβT1, peptides in which N-terminal methionyl residues are peptide-bonded to αT1 and βT1, were prepared by the solid-state method of Merrifield. These synthetic peptides were used to establish conditions for chromatographic purification and analysis. When tryptic digests of nascent globin chains from rabbit and sickle-cell anemia reticulocytes incubated with 35S- and 3H-labeled amino acids were analyzed, radioactivity not present in tryptic digests of labeled hemoglobin appeared at the elution positions of MetαT1 and MetβT1. The fraction of nascent chains with N-terminal methionine was higher in sickle-cell anemia reticulocytes than in rabbit reticulocytes. If rate of peptide-chain elongation in polysomes is uniform, nascent human chains must attain a greater length before removal of the initial methionyl residue. Length of nascent chain at time of removal was calculated from two independent sets of data, one obtained from [35S]methionine incorporation into MetαT1, MetβT1, αT5, and βT5, and the other obtained from [3H]lysine and [3H]valine incorporation into MetβT1 and βT1.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=433665Documentos Relacionados
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