Differential processing of human and rat E1 α precursors of the branched-chain α-keto acid dehydrogenase complex caused by an N-terminal proline in the rat sequence

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Abstract

The N-terminal sequences of the E1 α, E1β and E2 subunits of the human branched-chain α-keto acid dehydrogenase complex have been determined by microsequencing. The N-termini of human E1β and E2 subunits (Val and Gly, respectively) are indentical to those of the corresponding rat and bovine subunits. However, the N-terminus of the human E1 α subunit (Ser) is identical to bovine, but differs from the rat E1 α (Phe0 subunit. Comparison of the N-terminal sequences of human and rat E1 α subunits shows that the serine residue at the + 1 position in the human sequence is replaced by a proline residue in the rat sequence. The presence of the proline residue apparently causes a 5′-shift by one residue in the cleavage site by the mitochondrial processing peptidase in the rat sequence, when compared to the human sequence. The results provide evidence that the mitochondrial processing peptidase cannot cleave an X-pro bond, similar to trypsin, chymotrypsinand microsomal signal peptidases.

Original languageEnglish (US)
Pages (from-to)125-128
Number of pages4
JournalBBA - General Subjects
Volume1201
Issue number1
DOIs
StatePublished - Sep 28 1994

Keywords

  • (Human)
  • Alternate cleavage site
  • E1 β and E2 subunit
  • Mitochondrial processing peptidase
  • N-terminal sequencing
  • X-Pro bond

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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